Yes, intra day movements (made within the day) are not counted with (most) banks. Meaning if salary is paid and taken out same day, there is no net change
I actually put money in twice on 2 separate days.
First time was straight forward for me.
Second time on a different day, I put in an additonal amount but withdrew it on same day (as I misread that the promotion was for a one off).
Subsequently after clarifying, I re-deposited. It took a while (Saturday deposit, Thursday earmarked and they confirmed the date of interest would start from the day of deposit).
You do need to enrol per the eform
https://internet.ocbc.com/internet-banking/Login/Login?rp=/internet-banking/OnlineForm/Form?FormId=CASATopup2025&redir=1