Hey again I guess you're applying for the free transit visa based on your message.

Port of departure = Cochin
Final destination = Where you're flying to next (e.g. Singapore)
Flight details = Your inbound flight from Cochin to Colombo

They only ask for flight details so they can gauge how many passengers will arrive in certain periods, i.e. if there's going to be 500 pax arriving between 10:00 and 11:00 they can get extra staff on desks. It's not uncommon for people to change their flight and arrive at a different time/date, the data you provide is purely for statistical purposes. So don't worry.

You're supposed to print off a confirmation of the ETA (and I'd recommend doing so), but I've never been asked for it at immigration. Just hand over your passport.

Btw, there's also an arrival card to fill in too, and I've never seen any pens at the airport. So take a pen to fill in the card, otherwise you can't proceed through immigration until you find someone with a pen!