Can anyone help re esa3(ibr)06/18 form

Hi, I hope someone can help.  I received my form in the post this morning informing me that I am currently on contributions based esa.  I have been on this and before that incapacity benefit for many years.  I was widowed at 42 and in receipt of my husbands pension.  I was told that the pension was not taken into account when claiming esa (C) as it is an inherited (survivor pension) and is disregarded when calculating ESA C but will it be the same for IR?  There is nowhere on the form I got this morning other than a tick box at the bottom of the pension section asking is this pension inherited.  If I tick this will they understand that it is a reduced survivor pension and is disregarded for esa C and does that mean it will be disregarded or not when calculating income related esa? so confused! Many thanks x