Your else statement is a call to isdigit function, and you discard the result. The block statement that follows is outside of the if-else statement (whose if part isn’t shown) and is thus executed regardless of that condition (which isn’t shown).
else will be executed and check if it is a number if it is then …
In order to do something if some condition applies, you can use an if statement. You can have an if statement within an else statement.