Snare is right...to an extent.
You should be able to add a callout like 6X within a basic dimension box. Solidworks does not allow this.
But usually this type of callout in used for angular dimensions only, never for linear dimensions.
When snare used the term "user text", the first thing people think of is some sort of note which is not allowed.
Remember...
"If you don't use your head,
your going to have to use your feet."