How does useTracker observe a collection

Hi, I’m trying to understand how does useTracker observe a certain collection and update in a real time
Lets say i sub to a publish method that returns a cursor of a collection called Messages

With every new message that is added to the collection i can see it on client because im subbed to that cursor

how does useTracker combined with sub/publish work?

and this brings me to the real question i have, If i sub to only 10 data, and i send over the wire to the client only these 10 datas,

I will never be able to know what is the size of the collection, since im limited to 10, and if i create two subs, that means i sub to all data, and then sub to 10, then whats the point? i already sent all the data and i can simply use find on client

however i want only 10 to be sent over the wire and i want to have the client listening to the collection whenever its updated to bring the whole size and be updated in real time as well

is such thing possible?

You can subscribe to counts as you subscribe to data. Just try to understand the size of data you subscribe to, to make sure things don’t go south after a year or two.
Initially, counting 1000 records might be lightning fast but as you go, 1 mil records may be dead slow if the count criteria is complex.