@Andrea9 - Fair point - and I should have focussed more on the original post main question of whether there will be a penalty for declining the alteration request........ And your question of whether a person can use the Resolution Center more than once..... good one, and I do not know for sure, other than I know it has been used for several additional requests during one booking (for kayak, bicycle rentals during a stay).
@Tania-and-Andrew0 I think your first response at this obvious attempt to get around your 3 night minimum is to reject their alteration request as @Andrea9 mentioned, then the system should allow you to send back another special offer or alteration request for the 1 night at the price of 3.
If you have time - contact Airbnb via Twitter (#airbnbhelp) and ask them for advice or support for a no penalty alteration.
Best Wishes. And please let us know what happens, because I have a lot to learn!