I did a full backup of a drive that has 18 GB worth of data on it.

Then I setup an incremental backup to execute 2 minutes later. It created a 13 MB file. Then I modified that scheduled incremental backup to happen about an hour later and it created another file this time 50 MB big.

Does it start overwriting files after a certain amount of time?

If it continues like this it seems it eventually will fill up the whole drive.

I thought the point was you could setup a schedule to backup your drive every day and you wouldn't have to mess with it or worry about it filling up your whole external HD and then not backing up anymore.

Would there be a way to have it create 3 seperate backups that happen like every third day and for it to overwrite the full backup instead of continually adding files?