This is excels way of telling you that the field does not fit in the cell.
If you make the cell-width "automatic," the hashes will dissappear.
This generally happens when you give a cell a specific format and Excel feels it doesn't fit in view.
EDIT: To make your cells auto-width:
Double-click on the right edge of the column header. That is, at the top, you have columns A,B,C... Say you want to expand the values in column E. You have to double-click on the edge between columns E and F.
This will expand the cell size. Also, if you have text in the cell, you can always right-click on the cell, click on Format Cells, and then put a check next to Wrap-text.
I wouldn't be so bothered by this, except, when you copy the cell and paste it somewhere, it pastes the ##### hash marks instead of the actual masked value! This is extremely frustrating, because I have to make sure the cell is wide enough to display the actual value before I can copy the value. – ADTC – 2017-03-22T03:38:42.943