You're welcome, my dear. I thought you might want to have something meme-like thrown in the mix.
Those fingers are the magic flutter over there keyboard. Ha, ha, ha. I see they work just fine. Well, more than that.
About the chord, I think it was that Eb with the augmentated 5th. You played Bb and then corrected it immediately. I guess it's hard to wrap the brain around these changes. But that's what study session ought to do.
Keep calm and study Rachmaninoff. I might dust off the Vocalise. It is a very nice piece.