[{_id:"5 becomes 10",counter:5},{_id:"9 becomes 10",counter:9},{_id:"10 becomes 11",counter:10},{_id:"11 becomes 12",counter:11}]

db.collection.update({/** select specific docs if required* _id: 1*/},[{$set:{counter:{$max:[{$add:["$counter",1]},10]}}}],{multi:true})