You can do this based on a custom method. Add this at the bottom of bot.cpp: 
	Code:
	uint8 Bot::GetMaxBots(uint8 level) {
    if (level >= 1 && level <= 9)
        return 1;
    else if (level >= 10 && level <= 19)
        return 2;
    else if (level >= 20 && level <= 29)
        return 3;
    else if (level >= 30 && level <= 39)
        return 4;
    else if (level >= 40 && level <= 64)
        return 5;
    else if (level >= 65)
        return 71;
}
 Add this in bot.h: 
	Code:
	uint8 GetMaxBots(uint8 level);
 And change this line: 
	Code:
	if(spawnedBotCount >= RuleI(Bots, SpawnBotCount) && !c->GetGM())
 To this: 
	Code:
	if(spawnedBotCount >= GetMaxBots(c->GetLevel()) && !c->GetGM())