By default the maximum characters allowed for the STRING data type is only 16. It can be increased to 65534 ASCII characters.
For this select the data type as STRING [<size>], where size denotes an unsigned integer (UINT) capable of defining a string between 1 and 65534 ASCII characters.
The result will be displayed in 16 characters only. However, the maximum characters it can contain will be the one defined in it's data type.