I left my digital probe thermometer switched on on a kitchen worksurface and noticed it read 27 deg C. Kitchen is cooler than that so I compared it to an outside thermometer. Conclusion - it is reading 10 deg C high. I mashed at 69 deg C so in reality 59 deg C. I used 6 lb pale malt with a final volume of 3.5 uk gals having OG 9 Brix. Yeast pitched was Nottingham. Any guesses how the beer will turn out, I will give feedback in 4 weeks or so. I have ordered a new one with a shorter probe. I intend to calibrate against that each brew day but use the old thermometer, providing it is consistent error.