During my test cruise after bleeding the drum brake, I was getting the "parking brake" red light blinking, flashing, being quite annoying. Worried that I might have introduced a leak in the system, I stopped to look at fluid level in the reservoir. It was above the "MIN" marking, about where I'd left it. I may have done myself a slight mischief when putting the cap back on. I didn't pay any attention to holding it vertical until the threads engaged. My theory is that canting the float in this way caused it to ride lower and signal low level prematurely. Got a "torch" and a magnifying glass so that I could find the "MAX" mark, topped up with DOT 4, and kept the float stem vertical while putting the cap back in place.