Betor’s last ability will check as the end step starts to see if creatures you control have total toughness 10 or greater. If they don’t, the ability won’t trigger at all. If it does trigger, the ability will check again as it tries to resolve. If creatures you control don’t have total toughness 10 or more at that time, the ability won’t resolve and none of its effects will happen. The ability won’t check to see if their total toughness is 20 or greater (or 40 or greater) until the ability resolves.