Henk....It sounds like you have the 1 user authorization that comes
with the base server plus you added the 50 user authorization feature.
You can have the server support as many clients as you like.  To license
them, you can add them in the increments you mentioned--1, 5, 10, 50.
You can have as many of each of these features as you like to add up
to as many clients as your server will support.  It sounds like you just
need to order the additional client feature(s) and then issue the
appropriate REGISTER LICENSE commands (then the AUDIT LICENSE command).
If you need to add 5 more clients (above your 51 you are currently
licensed for...purchase the 5 client feature)...if you need another 50,
purchase the 50 client feature again (you can specify the quantity of
each client authorization feature).

hope this helps...greg tevis, adsm technical support