open X:/Battlefield2/mods/bf2/AI  
set your mod(X:/Battlefield2/mods/???/AI)
open AIDefault.ai
find:

=============================================
rem Example for 32 bot game with expert bots  

rem aiSettings.overrideMenuSettings 1  
rem aiSettings.setMaxNBots 32  
rem aiSettings.maxBotsIncludeHumans 0  
rem aiSettings.setBotSkill 1.0  
=============================================

delete "rem" ,like this  
 
=============================================
aiSettings.overrideMenuSettings 1  
aiSettings.setMaxNBots 64  
aiSettings.maxBotsIncludeHumans 0  
aiSettings.setBotSkill 1.0  
=============================================

ok setMaxBots is BOT number,if we want 63 bots  
aiSettings.setMaxNBots 32 turn aiSettings.setMaxNBots 63 
(max 256 bots) 

the aiSettings.setBotSkill 1.0 is BOT skill,best 1.0  
