Customer Numbers

For customer numbers in manual order entry, there appear to be 3 options:

-          Auto-sequence
-          “Free-text” (enter your own #, no default)
-          Auto-sequence with override.  (A number is given, but you can change it)

In manual entry using the last option, it appears that if a new number is entered, the next auto-sequence default will follow from that number.  e.g. If the auto-sequence number is 100, and you enter 300, the next auto-sequence number will be 301.

We would like to have one sequence of customer numbers running for manual entry, but a different sequence of numbers for customers created via our webservices call.  (The numbers created via webservices are maintained by our external system.)  Our concern with this is that when a customer is created by webservices, the next manual customer number will follow from the webservices customer number.  Is this actually the expected behaviour?  If so, is there a way to avoid this, either as a NetSuite setting, an option on the webservices call, or some other method (e.g. making our customer number non-numeric by