This shouldn't make a difference. Prime converts ammonia to harmless ammonium, but both ammonia and ammonium will register as "ammonia" with most test kits. There is so little ammonia in the tap water that the normal amount of Prime (for the volume of water being changed) will work OK.
Originally Posted by Zerileous
Overdosing of Prime or any water conditioner is not advisable.
Byron Hosking, BMus, MA
Vancouver, BC, Canada
Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]