Chris Kresser on Joe Rogan cited this fact, stating that this figure includes everything from direct animal deaths to birds eating insects that are filled with toxic levels of pesticides. Furthermore, this is more than the number of animals we kill "We're not killing 7 billion cows". This paper is cited
We slaughter nearly 10 billion land animals in the US. So even without the nearly 40 billion marine animals (and their bycatch) or plant agriculture deaths to just feed the livestock, already we're at more deaths from just the direct killing of animals. This is acknowledged by the authors of the paper themselves. So that part of the claim just isn't true.
The authors of the paper state "... but two things are clear. First, the estimate should be reduced: 7.3 billion is clearly too high. Second, we should have a fairly low level of confidence in whatever number we propose. There are too many reasons to be skeptical about generalizing from the available data, which is obviously quite limited in its own right."
So clearly these authors disagree with Kresser's assessment of their results.