Confused over patio door pricing / manufacture

I’m in the process of a patio door replacement with Lowe’s and I’m a bit stuck. The consultant came to the house for a measure and the guy who came measured the width at 59.5” and the height at 81.5” and said it would be a custom size. He also gave us a quote and sent a contract with a price of $3600, which I signed. Then they sent a contractor for a second measurement and they measured at 59.5” and 80.5”. Lowe’s is now telling me the first contract is void with the updated measurement, and also that the project will be $500 more because of the sizing being custom. They already said it was a custom size, so I’m a bit confused how a door that is an inch smaller would be $500 more. Not to mention on the callback, he tried to sell me on a no-interest promo with the Lowe’s credit card.

I also am having difficulty believing that when my condo complex was built, the builders would have chosen odd-size doors for all of the units. I have a feeling the door I currently have is a standard size and they’re trying to find a way to sell a custom door by saying it’s a half inch off standard size on both width and height.

Does this sound right? Or is Lowe’s trying to squeeze money out of the project?