Full Snapshot not being created

I’ve just migrated from SD to SSD on my RPi3 after the SD failed. I had a Backup from 4 weeks ago so I’ve had to rebuild from that point forward. I’ve made a full snapshot of my new system (now on version 0.111.3) and gone to copy it to my PC using SambaShare.
The problem is my 4 week old Backup was 96kB, whereas the ‘full’ snapshots now being generated are around 2kB.
I can’t believe these are comprehensive backups so what is going on?