As zorkian noted, "messages per day" is a marketing number. In a technical blog post, what matters is the numbers which are relevant for technical purposes, such as peak (or high-percentile) messages per second.
1) avg mean (for throughput estimates),
2) p50 (typical customer / typical load),
3) p90 / p99 / p99.99 (whatever you think your tail is)
4) p100 (max, always useful to see and know, maybe p0).
Or throw in a histogram or kernel density estimate, sometimes there are really interesting patterns.
I’ve never seen a technical blog give such traffic or latency details though.
Edit: reading other comments, please do not read this as diminishing this blog post or Discord, great clear writing and impressive solution to an interesting problem.
Useful for what exactly? You're basically accusing the company of inflating their numbers (??) as if they are deliberating lying about their scale.