size

what are those numbers referring to?

iPhone models would be iPhone 6/6 Plus, iPhone 6s/6s Plus, iPhone 7/7Plus, etc..

If you go Settings > General > About, what is your iPhone Model?

Identify your iPhone model - Apple Support

If you're referring to screen size.. an iPhone 12/13 Pro Max has a screen size of 6.7", an iPhone 12/13 Pro has a screen size of 6.1"

You can play with the models and see screen size here

https://www.apple.com/iphone/compare/?modelList=iphone13pro,iphone12promax,iphone13promax

you're not looking at it correctly. The link I provided shows a 13 pro, then a 12 pro max and a 13 pro max. Both of the max models have the same screen size and it's the 6.7"

or... you're saying that the seller gives you an option of 6.1 or 6.7 when you select a max model?

If that's the case, then I agree, it's confusing and you should try to contact the seller?

Use the link that Chris0107 provided above to look at the technical specifications for the iPhones to see the screen sizes.

Iam trying to order a phone case it’s asking 6.1 or6.7 before I ordered size for 12 promax