What I described with the 7, 40, 1000 (and now 12) etc was an example of why extra-biblical comparisons skew the results (tend to give a false-positive signature indication) - ie an example of what not to do.
IMO, what to do, is to decide (lol) where God's signature is to be found; in the words & letters, or in only the text attributed to God speaking, or in pronouns and verbs only, etc., and what that signature might look like.
Then apply that test of what it looks like in every place it ought to appear, and let the 'signature theory' live or die on those results. We don't tweak special-case signatures for different parts of the bible - unless we believe God tweaks His signature everywhere. So, the criteria for a 'signature of God' is defined and vetted, consistently, intra-biblically.
If the theory bears out, and a 'signature' seemingly is found consistently at least everywhere we expect it, then apply the same test extra-biblically to presumably show the test failing extra-biblically - because we assume God didn't 'sign' extra-biblical texts. If we find God's signature extra-biblically, then it probably wasn't God's signature in the first place, even in the bible, and we go back to the drawing board.
Note the distinction here is the criteria is first defined and vetted in the bible only. What may or may not exist elsewhere does not 'taint' the definition of the criteria as it is being developed. And then only successful signature theories are further tested for confirmation (anticipating true-negatives) against extra-biblical writings.
IMO, the real signature of God is actually found in His prophecies.
God's signature of authenticity is in His foreknowledge revealed in a prophetic passage. Only God has such foreknowledge and only God can ensure the revelations are given consistently to many people across centuries of time. Note how *none* of that could possibly be of man, even though the divine dictation was taken by man, ie man can't forge (or falsely detect) such a 'signature'.
We can test fulfilled prophecies to see if they come true (they do). We can test unfulfilled prophecies to see that they must yet be future (they are). We can apply these tests to every prophecy in the bible (consistently), and compare them against the historical record (we have).
We can then check extra-biblical writings to see if they likewise come true. Almost all extra-biblical writings lack prophetic passages, and those that have them generally fail to come true, or are so vague as to be untestable (no signature).
Ergo, God's bible is authentic. His signature being in His prophecies, and His signature (and prophecies) being found nowhere else.
But there are other fulfilled prophesies as well such as Daniel's concerning Alexander the Great, etc. - and modern day fulfillments, such as the return of the Jews to Israel with language and tradition - after being spread among the nations for nearly 2,000 years.
But there is also God's trademark in the heavens and the firmament (Psalms 19). Science itself runs headlong into such declarations of His glory - e.g. that there was a beginning, the existence of information in the universe and biological life and more.
And there are also signatures in the Scripture. The most obvious is the single Authorship despite it being compiled over centuries by scribes of different backgrounds.
The natural man can see the continuity throughout but more importantly, the Scriptures themselves bring the living Word of God alive within the reader who is born again. The Scriptures are not like any other manuscript.
There is also a mathematical consistency in the Scriptures and nature which suggests that an authorship trademark may exist either in the meaning (like Seven_0's posts) or in the actual language as dictated by the Spirit (e.g. the ELS in Genesis) - or both.
That there is a mathematical structure should not surprise us, since God created the natural world and also authored the Scriptures.
The mathematical structure of "all that there is" is so breath-taking that the physicists refer to it as "the unreasonable effectiveness of math". For instance, it doesn't surprise us that calculus can solve physics problems - but it is positively breath-taking that Einstein was able to pull Riemmanian geometry off-the-shelf to describe general relativity. Personally, I also see this is a signature of God the Creator.