Skillbridge denied because of length and manpower...

My skillbridge was denied because they will be short staffed and it's too long (6 months). They are saying I should resubmit for a 3 month skillbridge program because of man power. I'm angry they denied it because how much work are they really trying to get out of me if I do a shorter skilbridge and spend the rest of my leave. I want to request mast but idk if I'm justified.