ESA contribution based and occupational pension pa

Hi magic moderators, hope Gordon is enjoying hols .
I am in receipt of occupational pension since 2006. The amount I get slightly increases each year ,working out to a few pounds rise a week ,I've told job centre about this payment from day one , so nothing to hide an each year they send me a letter requesting evidence of what I'm currently being paid. My pension is small it started at £80 a week originally now over the years it's up to £95. In previous years I've had to pay tax on this , but then the tax brackets changed , so I know longer was requested to pay anything and hmrc said they'd inform my pension provider if I was to have deductions made, however I've not had any . However my worry now is that I've only just realised this £85.00 ruling on ESA payments for people in receipt of pension. Since 2017 ESA have only deducted 19 pence a week from my payment ? I didn't even notice it an naively never fully read the usual bog standard renewal letter I get from them every year. They have written to me in May this year as they usually do asking for proof of pension payments , I have obliged . So now I've come across this info about the deduction they make , I obviously am not strangely being deducted the difference as I see it ? Can't fathom out where they got the 19 pence from? .
When did this £85.00 ruling come into force?
Can they back date what I think I should technically have been deducted, even though they were fully kept up to speed an have been making a deduction?
I'm currently still awaiting on decision on my esa50 form submitted May 14th, so I'm totally baffled an worried about being stung with a huge bill.
Any info or help will be gratefully received, cheers

Cheers Gordon ,ill work it out again an maybe things will make sense? I thought you were on hols? Lol. You really are a genuine help to many people.
So if they come back at me an try to claim overpayments, can I tell them were to go? Lol.

Sorry Gordon me again, I've just worked out weekly payments again for tax years 2016/17 17/18 on both accounts I'm over £85 slightly firstly by £1.33 a week then by £4.16 per week so by halving either amounts I still can't fathom how they got to 19 pence? Hilarious? So now I'm worried, should I act or play dum? Do you know when the £85. Cap came into play ? Thanks . Sorry to go on.