Question about being awarded SC vs assigned.

I put in a PCS request to be awarded SC for tomorrow. I ordered my SC time preferences 1800-2359 then 1400-2000. Is was awarded 1400-2000, however they assigned a 1800-2359 to someone senior to me that was in the same raw group with the same days of availability. Shouldn't I get that 1800-2359 since I put in a PCS request over an SC assignment ??

Hardly ever sit reserve, so not super smart on the nuances....