Homebase 2 only using 1%

Hi,
I hjave a homebase 2 and one camera. I have placed a 1Tb drive in the homebase and it has been recognised and formatted. The Homebase reports 99% available, and has done since I installed it, however, it delets videos more than a month old. How can I force it to keep videos, and only delete the oldest ones when the disk is full?