Originally Posted by stut

That's pretty much it. It translates as:

1 seat, coach 256, seat 76, window, open carriage, non-smoking

Naturally, the train won't have 256 carriages, but the numbering can reflect where trains need to split. There will usually be some means of determining where on the platform to stand, whether electronic or paper.

Open carriages are the corridor style, as opposed to compartments.