ESA result or not ?

Hi Gordon and hope you are fine,
My husband sent his ESA re assessment back approx 3-4 weeks ago, he has received a letter and not sure if it’s a result or annual letter as it doesn’t say directly about the re assessment, my husband was in the support group already it does say on it:-
“Your claim for ESA changes in social security benefits, from April rates may change etc. Etc.
WHAT TO DO IF YOU THINK THIS DECISION IS WRONG
Please get in touch within one month etc. etc.
You can appeal and look again. We call this a Mandatory Reconsideration.”
Then it lists his ESA entitlement and does say support group in this
Questions:-
1. Should I ring the number on the letter and ask if this is a result,
2. What do I need to ask them as regards finding out the length of time for award,
3. it would be good to know how they came to this decision, what I should ask from them to send out to my husband as regards result.
Thank you once again.