As far as I know, each Soti MobiControl server implementation (irrespective of the number of  deployment server included) uses one reg-code with one expiration date.

If you have two reg-codes, you can use them in two totally independent MobiControl implementations.  If your initial intention is to just add more devices to the same implementation, you should have informed the sales personnel to get a renewed reg-code that include both your existing and new device license counts.  The only constraint is that all device licenses, existing and new ones, should  be aligned to expire on the same day with the new reg-code.  So, one can either :

1. add new devices to have the same expiration date as existing devices associated with the old reg-code  (this is relatively simpler)

or

2. have a new expiration date for both new and existing devices.  You have to pay for the full period for new devices, plus the extra period extended for existing devices.

So, unless you really intend to use two separate implementations, otherwise, you should contact your Soti account manager or reseller to arrange how to merge the two batches of paid licenses into one reg-code.