Backuptime Snapshot

Hi there,
Just installed SnapShot and that went ok and looks cool!
Two questions though:
1) I created a daily snapshot at 3 pm, Will the backup start each day at 3 pm? Is it better to create the snapshot at night? (As far as I can see I can't set the snapshot-time)

2) Wil it automatically backup ALL of my multisite sites (with mapped domains) when I select the rootsite?

Thx and cheers,
Ronald