What he is trying to say is that when an electric things, such as a ac, freezer, refrigerator, other things with motors, start-up they draw more amps than they do when running. Think of pushing a car on flat surface. Getting it rolling is harder than keeping it rolling. The generator you have will run at 3500 watts, IIRC, and can surge to 4000 watts for a short period of time.
I'm not sure what the starting amps of the ac is. If its more than 4000 watts or 30 amps, the generator will not start it. The blower will run, but the compressor might not. The other thing is that when something else is running and the ac tries to come on, you haven't got the full 30 amps going to the ac. You might only have 20 or 25 available to start the appliance, and maybe even less.
If the ac, which is probably the biggest load, starting amps is less than 30, then you are probably ok, if you haven't got a lot of things on when the ac comes on.
The larger generator would let the ac come on even if there were several other things running.
