You are right... Most of the times DF quota is released at the last moment... Eventually i might be wrong but excluding defence also (53 berths shud be available from PT after clearing CK + 2 PH + 1 FT + 13 LB sums to 69). 69 berths would clear 138 RAC passengers. This one is 139/140. There would certainly be 1 HO berths not utilized OR since couple of LB cancellations which would clear this.