Subdivision Surface Weights
You can select from:
Set exact values.
Add - each time you click on Set, a proportionate strength value will be added to the weighting.
Subtract - each time you click on Apply, a proportionate strength value will be subtracted from the weighting.
Use this setting to define an exact strength value for the weighting.
Clicking on Set will affect the strength value proportionally, depending on the mode selected (add / subtract).
Interactive Minimum [-100..100%]
Use this setting to define the interactive minimum weighting for vertices or edges.
Interactive Maximum [-100..100%]
Use this setting to define the interactive maximum weighting for vertices or edges.