
2 answers

I've answered my own question:
- This picklist is used for the Account records, for which we've defined several record types.
- For the Record Type that will be used for this picklist (Record Type = Customer), I went to username>setup>customize>accounts>record types.
- Selected the Customer type.
- Edited the Distributor field.
- Added the new values to the selected values.
Voila! Forgot all about the record type criteria being in the middle.