Every fuel type has its own stoichiometric value. But all your wideband cares about is lambda, which displays as 14.7 on your gauge. Lambda is the same for all fuels, optimally being 1. But your pcm is calculating everything based on 14.7. if you change this you will also affect other tables that either need to be changed or probably some that we don't have access to. So best to just leave it as is and tune as you would.