You’re off by 0.000000399999999955991114575226674787700176239013671875

(0.1 + 0.2 is actually 0.3000000000000000444089209850062616169452667236328125)

(And 0.1 is actually 0.1000000000000000055511151231257827021181583404541015625, and so on. People unfamiliar with IEEE 754 may be surprised by the output of python -c 'print("%.60f" % 0.1)')