Change size of stack formatting

I have a general table where I want to write with subscript ("OWA", where the A is in subscript). Previously I have been able to write "OW", and then use stack formatting, and choosing the appearance without the dividing line, setting the stack size to 50% and writing my letter ("A") on the lower stack.

Now I can't seem to change the size of the "A", whenever I select it and change the stack size to 50%, nothing happends. When I double-click the stack again to edit it, the stack size is back to 100%.

(First picture shows stack formatting with my settings, second picture the result I want).

The result shown was done in SolidWorks 2014, but in SolidWorks 2016 I replicate the appearance..