[{"agency":"AG1","year":"2022","month":"9","residents":[{"sequential":1,"name":"Resident 1","statusResident":"pending",},{"sequential":2,"name":"Resident 2","statusResident":"not analyzed"},{"sequential":3,"name":"Resident 3","statusResident":"not analyzed"},{"sequential":4,"name":"Resident 4","statusResident":"finished"}]},{"agency":"AG2","year":"2022","month":"9","residents":[{"sequential":1,"name":"Resident 10","statusResident":"pending",},{"sequential":2,"name":"Resident 20","statusResident":"not analyzed"}]}]

db.collection.aggregate([{$unwind:"$residents"},{$group:{_id:{agency:"$agency",statusResident:"$residents.statusResident",total:{$sum:1}}}},{$sort:{agency:1}}])