You want to exclude files A B and C by location, and their locations are, respectively:
C:\Data
C:\Data\Dir1
C:\Data\Dir1\Dir2
If you exclude C:\Data then you'll get rid of the first file but not the others, since their locations are not C:\Data.
If you exclude C:\Data* then you'll get rid of the second two but not the first, because there's no [b][/b] at the end of its location string. To exclude all three you need to use this wildcard:
C:\Data(|*)
If you want to exclude the Data directory on the root of all drives then you could use this:
*:\Data(|*)
If you want to exclude it only on C:\ and D:\ then you could use this:
If you are doing a Find, rather than a Sync, then you can use the subfolder clause to be more efficient. Excluding files by location doesn't stop Opus scanning everything in that directory because the test on the location is done after the file has been read. subfolder, on the other hand, prevents Opus from entering the directory at all and can thus save time. Unfortunately, subfolder doesn't currently work with sync.