There were a few different numbering schemes for SSE releases. These are somewhat speculative, however:
The 2000 series were techno/dance related.
The 4000 series were current, Japanese artists.
The 5000 series were licenses of material by foreign artists.
The 8000 series were reissues of material by Japanese artists. Many releases in the 8000 series were originally released by Transrecords (2).
There were also three samplers, numbered SSE-002 through SSE-004.
I have read about a 9000 series that was apparently for licenses of folk music from the British Isles. These releases may have simply been imported discs with an SSE obi added, but I am in no way certain as I have never seen one.