When testing for blood sugar...?

Some say to prick the finger,wipe it away and then take a second . Why what's the difference between the two amounts from the same finger (The finger was pre-cleaned w/achohol once before the 1st test as was the tester) The second amount was 95 as the 1st reading was 65. I took a third reading from another finger and that one was 75.Wich reading is the more reliable one?