Carb leakage.
You were correct. The fuel remaining in the carb bowl is disappearing. It is a common oroblem, and not too difficult to correct, The problem is the well jets are leaking. If you remove the carb, remove any remaining fuel by inverting over a container. Dis-assemble the carb, there are three main sections: Top or cover, center section and base. The leak occurs at the two aluminum rivets visible on the underside of the center section, when it is assembled to the base this section is in a depression in the base. An overhaul kit will give you a soft filler (like a sponge) that rests in this depression to seal off any leakage. It does not work. Use an epoxy (fuel resistant) and make a coating to cover the underside of the rivet section, use care and remember the base and center section must fit properly, it is not a difficult procedure. Before applying the epoxy eyeball the parts, you will see what I am talking about. It is not a great idea to allow this leakage to continue, it is flooding the manifold and cylinders whenever you stop the engine. After this repair is completed, the startup is fine. Be safe and enjoy.