Upfront margin collection changes - BOD

Hi,
SEBI has released a circular, SEBI/HO/MRD2/DCAP/P/CIR/2022/60, about changes to margin collection changes. Can someone simplify the change? Specially, what does “fixed beginning of day (BOD)” mean, is it that margin collected will be verified at “09:15” for shortfall?
Thanks!

Also pls clarify if there will be any leverage given like earlier?

Wrote a post on this topic in detail