1. ETA is from the first tracking when the parcel was accepted to the delivery to you. Into that you have to exclude the time the parcel is spending into Customs and Security of both countries. This should give you the Estimate Time of Arrival.
2. Now you should in any case also consider this:
Routing is a whole separate matter, but suffice it to say that “lowest cost” tends to win out over “fastest speed”. Mail shipments may transit many countries On Route to their destination.
Transportation delays are not uncommon — a truck may arrive late due to weather; a flight might be late because of a mechanical problem. However, many steps in the transportation process operate on a schedule. For instance, to get on a certain flight that departs at 11am, a parcel may need to reach the airport mail station by 1pm the day before. Missing a cutoff time means your parcel has to wait for the next dispatch, so it’s easy for a delay of a few hours to turn into one of a day or more.
Mail priority and volume:
If there is more mail than available space to send it, items of higher priority win out over lower ones. As a rule, express letter mail is the highest priority, followed by express packets and parcels, then ordinary letter mail, ordinary parcels, and finally SAL. So if you are sending a parcel via registered airmail, but there is a very high volume of EMS shipments that day, there may not be room for your item, and it’ll have to wait for the next flight.
During times of high mail volume, there is likely to be a backlog of shipments waiting to be sent. Your parcel, of course, starts at the back of the queue.
Finally, none of the above accounts for accidents, like your parcel being misrouted, falling off a conveyor belt at one of the sortation plants, or being mistakenly left in the bottom of a mailbag. None of these are routine or common, but they all do have the potential to cause delays of several days or more.
3. I would say within 3 weeks from the 17 Oct you should have receive your parcel.
Hope this help.