Why is it asking for more disks than the originally imaged

Imaged a computer successfully onto 5 disks. Replaced the hard-drive and re-imaged successfully again.
I had the computer repaired recently but ended up having the hard-drive wiped. No big deal I thought I'll just re-image again using the 5 disks that I used before. This time when I try to re-image Symantic 8.2 is upto 88% complete and looking for another disk. Why am I being asked for more disks then it took the first time I re-imaged? Is there something I need to do differently?