Fast Break

When you mine block your client sends 2 packets: when you started digging and when you finished. Due to ping problems time difference between 2 packets can differ between client and server. To make block dig rollback more rare server weakens rule, and doesn't check exact time. We can abuse this and always send 2 packets quicker.
This hack cannot make "non-instamineable" block instamineable. Instamining has strict check on the server.
Factor
1=no change, 1.2=1.2x faster and so on. Maximum theoretical value for vanilla server: 1/0.7=1.428571. It is better to use lower value.
When player is not staying on the ground minecraft sets penalty for digging speed. This penalty is applied during Fly Hack. You can disable this penalty, but you need to set OnGround = true in Fly Hack settings.