Is there a maximum number of user defined fields (UserProperties) that can be synchronized with GC ?

I added 2 different Fields using the .Add Method, one on the Contacts folder, and one on the Inbox folder.
The synchronisation works fine with the Contacts, but not with the MailItems. The new field is not listed in GC, although some other user defined fields are.

And what does the number next to a user defined field mean?

Thank you!

Info:
OL 2003
Exchange Server 2003 (SP2)

GC:
Multi User Business License
Version:4-2000(400801) Multi-Byte build.Outlook version 11.0.0.8169

Hello,

there is no maximum.
Please see help topic:User Defined Fields

number is Outlook datatype

I have a list of user defined fields DocSpec, DocNutri, DocMSDS it is defined as radio option. When I mapped with GC, It pull only "OptionButt" into the field regardless of the radio choice. Any Reason?

GeniusConnect will read the value of user defined field stored in Outlook, it does not know form definition (radio etc..)
Please investigate values of DocSpec, DocNutri, DocMSDS stored in Outlook.