SassError 90var--num is not a number81 │ for $val from 1 to $num

This error is occurring because the Sass compiler is expecting a number value for the $num variable, but instead it is receiving a variable named --num.

To fix this error, you should replace --num with a number value in the declaration of the $num variable. For example, if you want to iterate from 1 to 90, you can set $num: 91; before the @for loop.

Here's an example of how your code could look like:

$num: 91;

@for $val from 1 to $num {
  // your code here
}