Foreign Tax Credit Relief - enter total income or only the amount that was taxed?

I am a UK resident but have been taxed abroad. A HMRC advisor on the phone told me I must apply to claim this via the Foreign Tax Credit Relief section (box 2) on SA106. I'm unsure whether I should enter here the full income from which part has been taxed or only the amount that was taxed. For example, if I earned £1000 (converted from euros) in a foreign country and £400 (also converted from euros) of that was taxed in that country, should I write £1000 or £400 in box 2 on SA106? Thanks.

Hi,
It is the £1000 as it is the total earnings that need to be declared.
Thank you.