[Calahan]

It's WAD. As far as I know it is designed that way to represent the errors that can be reported from just a simple scouting act. As if you think about it, one guy hiding out in a province is very unlikely to be able to report back with exact enemy troop numbers. The best he can do is give a rough estimate of numbers and unit types.

Sometimes it will be reported that there is more troops than there really are, sometimes less. Can't say I know for sure what the exact error distribution is, but I'd guess anywhere upto 100% for small numbers of troops (and getting less variable percentage wise for large numbers).

If you want precise troop numbers, you need to use magic spells, such as Astral Window. Although spy units (which you say you are using) should provide more accurate info than simple scouts.