Slow trigger function execution

The first line of my function is:
var start = Date.now();
and the last line is:
console.log(Date.now() - start);
and I consistently see 6 or 7 as the result here. And in the Logs of App Services I see my function getting correctly triggered as type “Trigger → Database” (as the result of a new document being created). So this is all great.

But the runtime is always listed as ~ 10120ms (generally 10115 to 10125). Am I misunderstanding how runtime is listed in the logs? (I’m quite new to MongoDB.)