When you're brakes are worn down, your brake fluid level will go down as well. If for some reason he or you filled the brake fluid when it was low then once he puts new pads on... The fluid should overfill.

Does that makes sense? lower the pad = lower the level.

If you refill the level and add more pad, then it should overfill and spout out.

If the brake pedal seems squishy, bleed it and go from there.