December has roughly 15% untouched case + around 20% touched(RFE, RFER or pending) and 65% completed(includes approved, denied or rejected)
Technically December still have 35% left which is 1258 cases need to be decided.
This week around 120 December case completed, if this continue for future weeks, this will take almost 3 more months to complete all Dec .
All I'm saying is 60-70% of the case get a faster decision around 13-14 month and 30-40% of cases 17-18 months.