To clarify one thing - was this issued by UA as an S class ticket, or have you confirmed somehow that it is an SK S fare?

On UA (like CO) S is a relatively low economy fare class. If this is the UA fare class, then I would suspect that it would map to one of the discount SK fare codes on the page that sbm12 linked to above. If this is the case, then you could only earn 25% EQM and RDM...

If you want to know in advance, you could call SK, and ask them what booking class you're in. This can then be looked up on CO.com.