The phrase ‘not having allowed for’ means

Directions: Read the passage and answer the question that follows.

I climbed into bed and rolled myself in my blanket, first extinguishing the light that burned steadily near the door. I lay still, trying to get to sleep but my fear made that impossible and soon I sat up in bed peering into the darkness and occasionally glancing at the round window in the side of the ship, which seemed like a plate suspended in the darkness. For an hour, I must have sat like this, and then a draught of cold air suddenly roused me. I jumped out of bed; not having allowed for the motion of the ship, I was instantly thrown violently across the room.