Novice here, need help please!

Hi,
I’m trying to set up a simple calculation for a price based on length*width = price per m2.
The problems I keep running into is that:
1. despite that I keep adding min and max value to both length and width fields and then saving it, the numbers disappear, as if I hadn’t saved it.
2. then when I click on single line formula, despite that I do write in the price field: {width} *{length} , it doesn’t work when checking on the product page.
Added a screenshot here: https://ibb.co/yXNTvwx

Thanks for the help in advance:
A