You can't get more than 23 bots in the official maps. And some only 19 bots. This is because there are so many spawn points on the map. Spawn points dictate how many players (including bots) can play on that map. If you want more than that, you'll have to find maps that has more spawn points.

befitozi has a good idea there - CS Deathmatch otherwise known as CSDM. It's a plugin. Google for it. With CSDM you can keep spawning bots. However, the bots may not understand the deathmatch type gameplay and will still try to complete their objectives i.e. plant bomb/rescue hostage depending on the map.

My advice - drop the bots and come join us online.