@Jennifer1351 You have Smart Pricing turned on, you said? That's why certain nights are higher than your minimum. Smart Pricing raises them based on some mysterious algorithm. It shouldn't make them lower than your minimum, though, as @Emiel1 said.
I've read a lot about Smart Pricing on these forums, and I get the impression that when you set it, then start changing certain prices for certain dates, it can get glitchy and go below the minimum. I don't know that for a fact, though.
And in my experience if you use Smart Pricing, you shouldn't also use Price Tips. They just seem like oil and water.
That one dollar lower would drive me crazy and I would send a note via Twitter to @airbnbhelp and ask them to explain their math!