big time 真的的意思是很，不少，等于very much或者a lot。
You owe me big time because I helped you with your school project.
你欠我不少，由于我助你完成了学校的项目。
hit the big time的意思是大获成功。
After John hit the big time, he became very rich and forgot about all his old friends.
John大获成功之后，他变得很富有，把自己所有些老友都忘了。