According to this source, the total was fewer than 50 Confederate cannon, though seems to me I've seen other sources saying hundreds.
Anderson had 60 cannon, though only 21 available for use.
By the way, I notice from this source that Fox did send resupply boats to Fort Sumter, but they were turned back by Confederate fire.
So the intention was to send them again, in the dark on April 12.
That didn't work, only because of high seas, and by the next night Anderson had surrendered.
So the point here is: only bad weather prevented Fox from completing his mission to resupply Fort Sumter before Anderson surrendered on April 13, 1861.
Lincoln's resupply mission was far from impossible or unrealistic, simply suffered from bad weather & poor timing.
No good reason to read more into it.