Remove substring from a string

pcleslie

I want to remove a substring from a string (random position), I have try to use Detele() & DeteleStr but both can not return a string value just blank why?

I want get the following result

Before - [xxxxxx,xxxx]
After - [xxxxxxxxxx]

e.g. [fgdgd,gghg]

Delete('fgdgd,gghg',1,6) - no string return
DeleteStr('fgdgd,gghg',1,6) -no string return

By the way I don't know the difference between two functions