The Japan Travel by NaviTime app

I am using the "Japan Travel by Navitime" app to plan my train commute in Kyoto. If you have used the same app before please help with my questions. After i search the best train route from one location to another location, it usually will appear result with information like "Get on car 1-2", "Get on car : Middle", "Get on car : Middle / back", "Get on car : 6"....

Can someone explain to me about this limitation where the passengers should get on? And what happen if we get onto the wrong one?

Thanks.

That's just the closest cars to the exit. You don't have to ride in them.

For you to change trains smoothly,
some route finder tools show you the best position in your train.

For example,
when there is only one way at the station
for your transfer from Line A to Line B
and you need to go up to the concourse
from near Car No. 1 of the ten cars,
they show you this car number.

You can get on Car No. 10 at the opposite end of the train,
but that makes the required time longer,
which may result in your missing the suggested train on Line B.

The estimated time for you to make a transfer
may be practically too short for you.

For Japan Travel by NAVITIME,
you can change the length of the estimated transfer time.
On "Customize Options" Menu,
you see "Walking Speed" option.
Some other route finder tools has a similar setting.

Thanks Omotenashi and H for the explanation.