marathon preparedness?

I’ve been new to running (27F) this year and am running the NYC marathon this year! I’ve been following the Hal novice 1 plan pretty closely except for one off week where I was out of town. This week’s long run of 18 I fell short and only did 16. It was hard to imagine running 10.2 more miles after 16, I guess my question is with only 4 weeks left is it really possible to finish the race? I don’t have a time goal just want to complete, but after this weeks long run I’m not feeling too confident 🥲