PPI Barclaycard form information

Hi, Does anyone have experience of filling in the form for Barclaycard? They are asking questions for the date I took out PPI (would this not be the date the account started? Which I don't have the date for anyway!) They are also asking what my salary was ? Do they really need this information (I can't remember yesterday!) Too many questions has been putting me off and time is running out! Is there a cut off date of when you can claim from anyway - should I pick the earliest date (year) you can claim? I do have some old paperwork but the cards were taken out some 20 years ago - my paperwork is say 10 years old. Also the card numbers have I think changed once over the 20 years - will that make a difference?