Depends on your history really. The 10% isnt a hard rule. If your mileage is pretty low
Lets say you’ve been running 15mpw on 5days of running… or whatever number you pick.
If you’ve been doing that successfully for 3/4 weeks. Jack Daniels recommends to add a mile to each run day giving you 5 more miles that week.
Personally I increase my long run at a different rate than my foundation runs. like 1 extra on the foundation run and 2 extra on the long run.