Thanks for the feedback. I've topped up with DOT4 as the reservoir was practically dry.
Another dumb question, what is the second bottle on the drivers side engine bay for?
You are a very small amount away from disaster. The normal usage of brake fluid is very small and barring a leak, the only thing that reduces the level of fluid to a significant degree is wear on the brake pads. Cars I've had with new pads on 'max' were not at 'min' when new pads were needed.
While you have averted problems for now, on the face of it, the car needs attention to the braking system, both for a pad inspection, a look for leaks. and possible replacement of the fluid.
Second bottle is probably the clutch, most are hydraulic these days.
