I am in the same boat. I got the receipt number off the checks (VSC) EAC06xxxxxxxx and online status reads "your case was received 10/06".
But since I haven't received I-797 yet, I wonder if the RD would be different.
My take is
RD: the date when the package is received.
In this case, 10/06 is the date when an officer went through the package and accepted it. (not "approve"). Does this make sense?