Well I agree with @Admin too.
Obviously there is physical limit on the servers which InfinityFree hosting accounts use. It’s not like they have infinite storage however our hosting currently is not so big that we require lots of servers with alot of storage and most of our customers do not host too big websites on our servers either so I can say that there is no noticable limit.
We do not really measure limit however if for example someone made a file sharing website on our hosting (these are illegal) and if alot of files got uploaded to the service we obviously would have to take action.
Like @Kieran said there is small chance that you will get very popular anytime soon so do not worry.
We are managing everything 
Mike