Yes, you're going to need to do a large water change (whatever is convenient.. I usually only do big ones down to a point where I can stop before my filter intake would get air, so that I can just keep my filter running throughout the whole thing.)
You never want your ammonia to get up to the 8ppm level because that will promote the growth of the wrong species of bacteria in the filter and the setback from doing that will be a little worse than just a pH stall type problem. For you, at this initial staring stage you're at, this won't be a problem though as -no- bacteria have had a chance to get started yet, lol!
I personally don't like the use of these "ammonia calculators" as they seem to mislead so many beginners. Using an amount based on calculation *assumes* that one knows the real percentage of ammonia in the household aqueous ammonia that one has obtained and the *real* percentage doesn't always match what the label on the bottle says. Since its always advisable to test the dosing for the mg/l or ppm is produces, one might as well just do that to begin with. I just use a 2 gallon bucket and do a few tests and then multiply that up to the tank size. Even after that I try to come in a bit low on the first tank dosing and bring it up to the final 5ppm via a few adds and tests with written notes so I'll remember for sure what the final magic ammount of ammonia really is.
~~waterdrop~~