Pip mandatory reconsideration.

hello hello I applied for pip in march 2022 and got denied first time but have had my second appointment for a reconsideration last Tuesday, she said in 7-10 days I will get a letter with her Decision. My question is if I am awarded pip will the back pay be put in my bank first and then letter or is it true you can receive the letter and wait 3-4 weeks for back pay?