If 30% the target then the CG is only at 30% if it is it sits level when balanced at the point. For that airplane it is a safer bet for a first flight particularly in you are not familiar with that type airplane to set the true cg at 25 to 28%.

If the airplane is a single or double tapered wing then measure out half way from the fuselage side to the wingtip and measure from the leading edge to the trailing edge at this point. This will be roughly your Mean Aerodynamis Chord. Now divide this measurement by four and the result is the distance the target CG will be aft of the leading edge at this mid span point when shooting for 25% MAC.

John