According to KVS' tool SQ 886 has 7 seats across not 6 like SQ 16.
I don't know what the "legal" transfer time is but 50 minutes seems a little tight, especially considering that the OZ departure gates are usually on the other end of the SQ gates.
It probably would be o.k. but if it's not the legal connection time and SQ arrives late which is rare, you might have a hard time continueing on. The SEA flight on OZ isn't even daily.