Emmanuel is right. You might want to get familiar with the different kinds of syntaxes. Usually there are one or more matching rules for each syntax to handle the return of the appropriate search results. You probably don't want to use the integer syntax in the first place if you use this alpha numeric value. You'll get syntax errors from the server.
I highly recommend setting up a base ADS server and using the excellent studio tool available here to connect to the server and view the schema associated with the connection. The schema browser in Studio is excellent and will list all the different schema elements available to you as well as cross referencing them which is nice when you need to drill into which syntax is for example associated with a matching rule.
Most of the different matching rules are self explanatory but if you don't understand some just google for it to find relevant RFCs. This is what I do.
Lorenz Breu wrote:AFAICT, 'C785694' is by no mean an integer value ...
18.104.22.168.4.1.1422.214.171.124.27 is INTEGER, so i guess for equality you would want "integerMatch"
Can you please post user's question to the user's mailing list ?