The capacity is based on the cubic inches in the hollow plates. Some hollow plates are 1.25 or even 1.5" deep but most are 1" deep. A short stack filter press comes with 3 hollow plates, regardless of if it is 7x7" or 10 x 10". On a 1" deep 7x7 you get 49 cu " in each hollow plate, a 10x10 is 100 cu. ". As such a short stack 7" press gives you 147 cu" and a short stack 10" gives you 300 cu".
My press is a 7". I started with 3 sets of plates, but after a few years I added 2 more. Now with 5 sets of plates, I usually filter 30-40 gal/set of papers early thru mid season and it drops to about half that near the end of the season. The press I have could be further expanded by getting more sets of plates, up to 10 sets, but I'd need to get longer side rails to support the bank. A 10" will do just over double that.
If you find a press with deeper hollow plates, you'll need to do the math. The cu." is the key, the press keep filtering until all the plates get filled up with filter aid and niter.
My biggest year I had 1320 taps of my own and I bought sap from others to the tune of about 1800 more taps. My 7" 5 bank was nearing it's capacity only because I ran all my syrup to my 2x6 finisher and then final verified density and sent up to 60 gal at a time thru the press to barrels. In very early season I actually got the 60 thru 1 set of papers, but as I approached mid season it was definately 2 sets of papers. The only time I ran the lowest number of gallons was at or near the final clean-up at the end of the season. However I never had over 30 gal total after concentrating that but it took 2 sets of papers.
If you will be over 2500 taps in a short while, you may want to start with a 10" short bank, then expand as needed.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.