Binance Card - can I have BNB on card deposit for staking?

Hi all,

I hope you can help. I'm after buying a couple of BNB and was wondering must I keep them on a specific wallet in Binance to count towards the 30 average staking on the card or can I also deposit them on the card, without spending them of course, to contribute towards the cashback?

Also - if I buy 10 BNB today and make a large purchase tomorrow, in 30 days time will I get cashback on that purchase or is it only for purchases after the 30 days?

Apologies if this has been asked already but I'm not having much luck lately with search!

Thanks again!