The charge current should be set to medium or low and don't be surprised if the charger detects one or both of your cells as bad. The internal impedance of AAA cells is higher than that of AA. For this reason you may have to hold down the button for 3 seconds in order to force a charge.
In the end, this charger was "not designed for AAA batteries." So don't get mad at me if it doesn't work perfectly when using them in it. Also it does put a little force on the battery clips in a direction they where not designed for.