I make liquid soap from paste & my water % depends on how thin or “thick” I want the end result to be. For your 1st time making liquid soap, I’d recommend following a tried & true recipe that comes with directions & % listed for batch adjustments. I know I’ve seen one on SMF or at least a link to a good recipe.
If you're making liquid (KOH) soap with the usual paste method, the paste is made pretty much like an NaOH hot process soap. Most soapmakers use a 25% lye concentration for both.
When making KOH soap paste, however, the result is a thick jelly-like paste that doesn't pour. This KOH soap paste is later diluted with more water to make a pourable liquid.
There's no way to say in advance about how much dilution water you'll need. The amount will vary depending on the type of fats you used to make the soap, the amount of paste you want to dilute, the percentage of water in the paste, and your personal preferences.
There is at least one other method for making liquid (KOH) soap that uses more water up front to make a flowable liquid soap without having to dilute. I don't know enough about this type of method to give advice.