The numbers quoted will obviously vary from person to person, taking numbers from a message board post is not advisable. Get your optician to set the lenses up for you which he/she thinks are best in their test frame, then sight up on your pistol front sight. If it is clear and sharp then they have done their bit right and they will have obviously corrected for any astigmatism or other eye problems you have.
If they have any way you can set up a target at 6 yards or 10 meters to test the sight picture that would be even better, you should see a slightly fuzzy ROUND black over your pin sharp front sight. If there is nowhere you can set up a target then simply ask to aim at whatever round black dot they can put on the test screen for you. If it doesn't appear perfectly circular there is a problem with astigmatism which they will need to account for.
As other people and myself have pointed out a specialist optician may well do a better job being fully conversant with shooting themselves, but a high street optician should be able to get it right if you tell them what you need from the lens, perfectly sharp at arms length pistol front sight distance and slightly out of focus at target distance.
Everyone has different eyesight otherwise we would all be able to go and use supermarket glasses for reading, driving or shooting. Ask your optician what they think of reading glasses from the chemists, I bet they will have difficulty not swearing!