It means that your result is less than zero, but not within the precision
you are displaying. For example, if the result is -0.00000000142, and your
number format is two decimal places, you will see -0.00. Subtracting a
number from itself often results in something other than true zero because
computers convert to binary to do computations. Binary conversions are not
perfect when extended to 15 decimal places.

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Regards,
Fred
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"Herbert" wrote in message
...
Sometimes when I subtract a number from itself, I get a negative zero,
rather
than a simple zero. Why is this?