Pivot table strange result
 

I have a pivot table which displays the characters "ms7" instead of
the number 12 actually stored in the database upon which the table is
based. Any other number displays correctly: 11.9, 12.1, 8, 9 etc.
For instance, the number 12 is displayed as "ms7". If the entry is
changed to 11, when the pivot table is refreshed, the 7ms changes to
11. I just don't get it.