Just A Newbie That Found Some 1908-1940 Postcards

Hello. I want to introduce myself as a newbie who would like to discern if I have anything of value. As a perfect newbie test, I have found 2, 1c US Franklin green stamps...lol. So it has boiled down to either 552, 632 or 596. The question I have is about the perfs. I understand how they are measured, however, I am perplexed when looking at the Stiegle Auction pics of 596's...if they are perf 11x11, why do they all have an actual count of 11 holes by 13 holes? I get that the vertical is longer at 22.5mm but the ~3mm difference doesn't account for 2 extra holes...? Someone please explain. Thank you.

2 cm is the key and a perf. gauge. This is just a start. There is much more.

http://www.stampmasteralbum.com/Sta...nMeasure.htm