Work capacity assessment enquiry

Hi there,

I got yesterday my work capacity assessment decision which placed me in the LCWRA group, very grateful for the guides as so hard to navigate these forms when so unwell. I had a paper assessment although i was initially notified that I would have a phone assessment. In the decision letter (UCD81) is stated that I am placed in the LCWCA group but there is no information about the duration of the award. I will also get a backdated amount about 2 months (£687). I would really appreciate if anyone can help me to understand how backdating works and below is a timeline which i hope makes sense.

March 2020 fell ill with covid but tried to continue working from home for several months.
End of October 2020 - became too unwell to work so went on sick leave
Beginning of December 2020- I had an existing UC claim for a few months where I was earning £90 according to my wages. I updated the UC journal about reasons why I am on sick leave and asked them whether i need to upload my sick note but was told I don't need to upload it. I continued to be on sick leave with continuous sick notes till 29th July 2021 where my job ended formally on ill health grounds. During this time i asked again in the journal whether i need to upload sick notes and was again said no.
End of July 21 - I called UC to update about the formal end of my work and from this point on i was asked to upload sick notes which i did till the decision.

In the decision letter it states that we will backdate you up from the time you provided evidence with 3 months waiting so what i am trying to understand is whether it should be backdated form December when i informed them that I was unable to work but was refused to upload the evidence or the backdating is correct and should start from end of July where my job formally ended. I hope that makes some sense, its been a difficult and stressful process so I thought of checking in the forum before raising any enquiry with the DWP. Many thanks in advance.

Just saw the reply and I want to thank you for taking the time to write this. I will contact the DWP to clarify my award. Many thanks.