Why are different pages considered duplicates?

Question

Search Engine Optimization

Hello! The webmaster indicates that the page

/aksessuari-dlja-vannih-komnat-stellazhi/shirina/59-sm/

it's a double

aksessuari-dlja-vannih-komnat-stellazhi/shirina/70-sm/

Why? The pages are different. And how in this case to specify the correct 301 redirect, can you give an example?

Answer 1

And how are they different? Two characters in the url?
When there will be some (different) content, then there will be different.