There are 3 steps to calculating the handicaps for matchplay using one tee.
Step 1: Course Handicaps
For each player, convert their Handicap Index into a Course Handicap
Step 2: Handicap allowances
For individual matchplay, the allowance is 100%. This gives the Playing Handicaps
Step 3: Handicap difference
Adjust each Playing Handicap so the lowest handicap plays off zero.
Player 1 has index 11.2 and course handicap of 13, Player 2 has index 8.5 and course handicap of 10. Player 1 gets 3 shots and Player 2 plays off scratch.