How many slots do you have?
Can you choose which slot to save in?
You may have to add a 'delete save'. I don't use saves so i may be pulling this out of thin air. I would look at something like:
Creating a 'clear storage' button. On touched button (delete save) then choose which slot you want to delete. Again, i've never used 'save game' or anything like that, so i'm not sure of the logic that goes with it.
In my game i have 2 invisible objects, that when touched in sequence will clear my entire storage. This is only for testing purposes, but still in that general area.