Day 4 MTX blood results have actually gone down?

My day 1 hcg was 1159, had Methotrexate on Friday, got my day 4 blood results today which is sat at 605 (was 700 yesterday after a trip to the emergency department).

Is this normal, or just a sign it’s working? Could my body naturally have been trying to end the pregnancy?

I’m confused as they told me it would’ve likely gone up today before going back down, but it’s already dropped 48%.