How can I use >= right? Is (a+f()+c)>=0 wrong?

int he = 1;
vector<vector<int>> matrix { { 1, 5, 9 }, { 10, 11, 13 }, { 12, 13, 15 } };
bool bo=(he - matrix.size() + 1) >= 0;

I think bo is false,but it is true. I do not now why? Is it wrong for lvalue?