Yup, there's your problem... Generally, the brake system is designed so that if the pads are new and the brake reservoir is as 'max' - the level will drop to min when the pads are fully worn. Use it as a metal secondary check for pad life...I may have added some fluid since then, I can’t remember…..I look at my fluids all the time and sometimes add if it’s not at the max line. I’ve never seen a fluid line that satisfied me
And now you know to suck out fluid before compressing brake pistons - or at least be aware of the level while you work.
Clean up that brake fluid before it ruins the paint!