Test the color-fastness of the jersey by applying a small amount of the solvent on the underside of the jersey in an inconspicuous place.
Dampen a white towel in the solvent, and rub it on the back of the number. Make sure to moisten the entire area. Do not worry about over-wetting the fabric.
Flip back to the front of the number, and begin to try to lift a corner or edge. After it has been soaked with solvent for 30 seconds to one minute, you should be able to peel the number away. If not, re-wet and try again.