For whatever reason, zombie riot will only allow you to have half the number of bots on any given server. So if you have a 32 player server, you can only have a maximum of 16 bots spawned at any given time. Zombie riot will kick any surplus of half. You can get around this problem by using Source mod’s reserved slots feature. All you have to do is go to cstrike/cfg/sourcemod/sourcemod.cfg and edit the number of reservedslots under sm_reserved_slots.
For example, let’s say you wanted 20 bots on your 32 player server. Simply go to sourcemod.cfg and set sm_reserved_slots 8 and sm_hide_slots 1. In addition to this, you have to make a 40 player server to allow for only 12 players to be playing at any given time. There will be 8 hidden slots, and if you have a server that is pay per slot, well can’t help you there.
This is only a workaround for anyone wanting to have more zombies, but want to limit the number of players playing. Hope this helped! Enjoy Zombie Riot!