Take a look at the attached image, which is a screenshot from an excel sheet.
These numbers were programmatically written by a Java program.
When I first open the file to look at it, all the cells have that caret in the upper left hand corner. Double-clicking on a cell causes the caret to go away and the cell to become right-justified.
Is it the case that at first the cell contents are a String but then double clicking causes it to change to a number?