MathShark calculator wrong

Educational Insights EI-8490

calculator mode, adding decimals:

1.0001 + 1.2345678 = 11.234 (wrong)

1.2345678 + 1.0001 = 11.234 (wrong)

1.00001 + 1.2345678 = 11.23 (wrong)

1.000001 + 1.2345678 = 11.2 (wrong)

2.0001 + 1.2345678 = 11.234 (wrong)

1.5555 + 1.1234567 = 55551.123 (wrong)

1.5555 + 1.2345678 = 55551.234 (wrong)

1.9876 + 1.1234567 = 98761.123 (wrong)

1.001 + 1.2345678 = 2.2355 (weird truncation)

1.01 + 1.2345678 = 2.24456 (weird truncation)

.0001 + 1.2345678 = 1.2346678 (right)

.001 + 1.2345678 = 1.2355678 (right)

.001 + .2345678 = 0.2355678 (right)

something has probably gone wrong with binary coded decimal.

unrelatedly, CLR seems not to clear if the previous keypress was an operator.  it probably only clears if a number or = was previously entered.

123 + CLR

(CLR button does nothing.  "123" remains displayed.)

1 +

(displays 124)

CLR

(CLR button again does nothing, continuing to display 124.)