global variable type changes from string to integer?

Hi,

I noticed, that if to a global string-variable a string that contains a – (dash) is assigned, the variable becomes an integer-variable.

If I want to use this global variable afterwards to define e.g. a filter, an error is displayed that a string is expected but an integer provided. I am using text fields as a workaround. Any ideas why this happens?

Thanks in advance,

Julian