Yes, the sentence is grammatically correct. It means that the person reacted with a laughing emoji ("😂") on a video, prompting the speaker to question whether the person truly understood the content or humor of that video.
Here are a few possible rephrasings:
1. "You reacted with a laughing emoji on that video, so I was curious if you got it."
2. "Since you reacted with a '😂' to that video, I was wondering if you actually understood


