Hello, all right?
The estate border-Radius of CSS can receive up to four values.
Ex:
border-radius: 15px 50px 30px 5px;
The first value applies to the upper left corner, the second value applies to the upper right corner, the third value applies to the lower right corner and the fourth value applies to the lower left corner.
How are we talking about "/", a value represents how much will define horizontally and the other vertically related to that corner.
border-radius: 40px / 20px;
horizontal --^ ^-- vertical
Follow the image so you understand better:
I hope to have helped you, in case there are still doubts, follow the link to help you better:
https://www.w3schools.com/csSref/css3_pr_border-radius.asp
Opa valeu Roder helped well worth even hehe
– user139915