If the value "500 mm" is inserted into one of the Audit options, the value is overwritten with 5E+02. Why aren't the natural values shown?

The column "Values" displays non-ordinary numbers (via vertex position), but the limits of values for audit. That is, it is always either very large (~1000000) or very small (~0.0000001) numbers that contain a large number of zeros. Other values (1~5000) are allowed, but they have no practical significance for audit. 
For ease of reading and editing, these numbers are shown in the format "Scientific Notation".