You're editing a set of parameters something like this:
Then you change a value that causes the display to get wider and a scroll bar gets added to the bottom of the page, like this:
Then you click in the "Units" column and the table "scrolls" to reveal the units column which scrolls the "Value" column off to the left, effectively hiding it.
You can click on this tool bar button to recalculate the correct widths and restore the display so you can see both columns (assuming your physical screen is large enough).
Regards
Paul