Every time they add a new pool it increases by 100. You are alowed a max of 100 shares in each pool. 7 pools =700. Plus up to 100% bonus shares and as many shares as you want from delegations.
So if you max out at 700 shares you either wait for a new pool or delegate sp. 20sp = 1 share.

For exaple if you have 700 shares with 100% upvotibg bonus then delegat 200sp you would have a total of 1410 shares across 7 pools.

Jope this helps. Keep up to date on you current share by looking at the spread sheet.
https://docs.google.com/spreadsheets/d/e/2PACX-1vRhhnY8couo1lPKsOBLvwS1hfvVAlB6SrhAHWiM3qXOVep_AUenh97SyPAsMCBWH26HgCOrclNl31BZ/pubhtml#