[{"time":ISODate("1970-01-01T00:00:00Z"),"location":{branchId:1},analytics:{twilio:{additionalReminders:[1,2,3]}}},{"time":ISODate("1970-01-01T00:00:00Z"),"location":{branchId:1},analytics:{twilio:{additionalReminders:[1,2]}}},{"time":ISODate("1970-01-02T00:00:00Z"),"location":{branchId:1},analytics:{twilio:{additionalReminders:[1,2,3]}}},]

db.collection.aggregate([{$group:{_id:{date:{$dateToString:{format:"%Y-%m-%d",date:"$time"}},loc:"$location.branchId"},additionalReminders:{$sum:{$size:"$analytics.twilio.additionalReminders"}}}},{$group:{_id:"$_id.loc",appts:{$push:{count:"$additionalReminders",date:"$_id.date"}}}}])