about this mac > storage > backups is growing over time

I have a Timecapsule that I use time machine to backup 2 macs to. One of the macs concerns me because when I go to "about this mac", "storage" the value for "backups" is increasing over time. each mac has its own unique account one of them has zero for the length of backups, both appear to backup ok with time machine. Is the value for backups as indicated in the mac a sign that it's not being backed up to the time capsule? do i have a configuration problem?