I don't play GoldenTee, so I can't give you a number. Just try cranking it way down, then bring it up by 10% and test to see if you get any backspin. Keep bringing it up 10% at a time until you do, and then back it down again.
Or, if you have access to a real GT machine, pump some "testing" quarters in. Try to find a part of the game where you can make an accurate measurement of trackball performance. Again, I don't play GT, so I don't know if theyre's any part of the game where you can do it, you'll have to look. On a game like Centipede, you can place your finger on the leftmost edge of the ball, roll it stright across to the right until your finger hits the other side, and measure how far the shooter moves.