Reserve Golden Days

Are these seniority based or what? I did not get 2 of the 5 that I bid for. I’m 45% in category and asked for Sunday/Monday golden days following a 5-day stretch. Now I have to worry about a Saturday short call since Sunday is coded as an X day. My plan was to drop Friday making me unusable on Saturday but that is now blown up with them having the ability to nail me with a short call.
What did I do wrong?
Any suggestions?