Database
[{datetime:"2020-05-08 5:09:56",name:"namea",lat:55.826738,lon:45.0423412,analysis:[{"0":0.36965591924860347},{"5":0.10391287134268598},{"10":0.086884394}]}]
Query
db.collection.aggregate([{$set:{analysis:{$map:{input:"$analysis",in:{$objectToArray:"$$this"}}}}},{$set:{analysis:{$map:{input:"$analysis",in:{$first:"$$this.v"}}}}},{$set:{average:{$multiply:[{$avg:"$analysis"},100]}}}])