If your dimension has +/- you can select dimension and choose the plus or minus value. and thats the same for all dimension tolerances. Just choose the Tolerance value itself then done select when finished.
l was wrong before when I said limits could be added to a family table, they can not. Sorry. That sucks in my opinion. That should be a very easy thing for a family table to accomplish.
The only way I can think of to accomplish this would be to create parameters to represent the upper & lower values. Then add the parameters to the table, which will allow you to alter the tolerance from instance to instance. Then you will need to write relations to allow the parameters to be reflected in the actual model dimensions.
This is a very round about way to accomplish this, but it will work. I'd suggest you change to +/- tolerances, and just add the + tolerance & - tolerance to the table, just as robertd suggested.