Syntax Error SassError var--num is not a number

This error indicates that there is an issue with the way a variable is being used in a Sass file.

It is likely that the variable "num" is being used in a mathematical operation, but it has not been properly defined as a number.

To fix this error, you need to ensure that the variable "num" is defined as a number, either by assigning a numeric value to it or by using a Sass function to convert it to a number.

For example, you could define the variable as follows:

$num: 10;

Or you could use the "to-number" function to convert it:

$num: to-number(var(--num));