You may have seen numbers displayed as E+11, E+12, etc in an Excel cell, this is because Excel cannot display numbers with more than 12 characters. That includes fractions where the decimal places take it beyond 12 characters.
With the cells in General format, these are displayed as scientific notation with the beginning of the number and then E+11 (or the relevant number of characters). In this example from Row 8 onwards the decimal places have taken the numbers beyond 12 characters.
How can you prevent them? Simply highlight the relevant range, right click and select Format Cells and change them to a number format.
Another alternative, which may be more presentable for the end user, would be to use the ROUND function to round the numbers to a set number of decimal places.