I don't have access to Stateflow so I can't test this, but I know that the compound comparisons that you have shown are not allowed in Matlab, so I suspect that they aren't allowed in Stateflow either. The comparisons have to be done separately, then anded together. So, for example, change 0.90 < y < 0.91 to 0.90 < y & y < 0.91.
An example of why this might not be working for you, using Matlab code:
y = 0.1;
tf = 0.9 < y < 0.91
tf2 = 0.9 < y & y < 0.91
