'->' and robustness == 0

[FishMoun]

Hello, the tool is awesome, but I have faced a problem:
the example: '(a ==1) -> (b == 2)'
here is a testcase: 'a=1, b=10',

according to the doc:
''rho(phi == psi,w,t) = -|rho(phi,w,t) - rho(psi,w,t)| ,rho(phi -> psi,w,t) = max(-rho(phi,w,t),rho(psi,w,t))''
robustness of 'a == 1' is '0',
robustness of 'b == 2' is '-8',
robustness of '(a ==1) -> (b == 2)' is '0'
but actually '(a ==1) -> (b == 2)' is FALSE in this testcase

is this a special situation that it can't tell the truth value from the robustness?

Thanks.