Discrepancy between volume shown in Time & Sales, vs Volume. Why would the combined volume in T&S be way less than Volume shown?

Good morning!

I've seen some stocks where Time and Sales often doesn't match up with the volume.

For example, I was looking at SOS, and as of about 10:07 EST it was showing ~3600 total volume. Yet, when I added up all the Time and Sales since 9:30 AM EST, that only added up to 672.

Including shown in premarket starting at 8AM, it would be 709.

Am I misunderstanding this? Shouldn't combined T&S = Volume?