You are saying that the little horn ruled from 538AD to 1798AD or 1260 years.
What allows you to use 365.24 day per year instead of the 360 days per year that you insist on?
Here’s an excellent article, EXACTLY on point of our discussion. It is NOT written by a SDA, but it does quote Leroy Froom (SDA) and his supporting article.
The BIBLICAL PROPHETIC YEAR ITS LENGTH, ORIGIN AND APPLICATION
ZIONS TOWER of the MORNING TRACT PUBLICATIONS P. O. Box 28021 Detroit, Mich. 48228 1983
From the Conclusion:
In approaching the biblical prophetic year, the first task was to define its length, as determined by a comparison of related Scriptures containing similar time expressions. By subjecting these to a formal mathematical reasoning process, it was found that the prophetic year was equivalent to 360 days, and the prophetic month to 30 days.
The next inquiry, almost a parenthesis to the study, was to probe the origin of these lengths; that is, to consider how the Creator might have decided upon employing a 360-day year and a 30-day month for use in biblical prophecy. The conclusions, of course, could only be suggestive, since they are not positively stated in the Bible. Nonetheless, in correlating Scripture with naturally recurring motions of the sun, earth, and moon, certain relationships were evident. An average of the solar and “lunar” years yielded 359.80 days, and of the Gregorian and Jewish months, 29.98 days, almost identical with the prophetic 360-day year and 30-day month.
Here’s another article with similar conclusions. Also, NOT from a Seventh-day-Adventist as far as I know.
https://www.360calendar.com/find_New_Year_on_360_calendar.html
The 40-year cycles of the 360 calendar produces an average year the same as the Julian calendar, (365.25 days). This makes for easy conversions between calendars. However, the 360 calendar also has a leap-month correction every 4000 years (100 generations). This makes the 360 calendar just as accurate as our modern Gregorian calendar, which means that one can count backward and forward in time by increments of 4000 years and always know what our calendar year would be on the 360 calendar. Thus, the 360 calendar repeats itself on the Julian calendar every 40 years and on our modern (Gregorian) calendar every 4000 years. The 360 calendar can be further adjusted every 100,000 years (1000 generations of 100 years) for extreme accuracy, yet maintaining the simplicity of round biblical numbers. At this level (of 365.2422 average days in a year) it is out only about one day every 100,000 years. The calendar begins at the exodus from Egypt of Israel on 1446 BC.