ok im confused with the timing meter that i have. its a snap-on MT1480 lumy/mag ll. when i power it up with the magnetic pickup and the luminosity probe hooked up and a 20* offset, i can get two different readings depending on which way i turn the pump. if i turn the pump one way it will read like (neg 1.0) and if i turn it the other way it will read (1.0). which way is the correct way its supposed to read?