A drag is a friction clutch, so what it holds steady is a torque — and the line leaves from a radius that the fish spends the whole fight making smaller. The number you set against a full spool is not the number in the water two hundred metres later, and nothing on the reel tells you that.
↑↓ or drag up and down — the rod · ←→ or drag the strip at the bottom — the drag knob · R to start over