Attribution when both Sponsored Product and Sponsored Brand ads hit

Can someone educate me as I couldn’t find a clear answer?
I am new to Amazon Ads but been using Google (data-driven) for awhile. I recently added Sponsored Brand (SB) to complement my Sponsored Product (SP) ads. And I noticed that SB has been given most of the conversion credits. Its ROAS looks suspiciously high too …. like 2x of my average SP ROAS.

Assuming it is not counted both in SP and SB, the conversion is solely attributed to SB if customer viewed the SB ad after their last click of the SP ad. Is this correct? Thanks!