negative tensile damage

Hello everyone

I am trying to simulate small scale concrete gravity dam with plastic-damage constitutive model.
I use the linear concrete tension stiffening and concrete tension damage as shown below:

*concrete tension stiffening
22157      0
222         0.000685526
*concrete tension damage
0      0
0.9   0.000685526

The output of DAMAGET shows both positive and negative values. I don't understand why the outout give the negative value. The tensile damage should be 0-1.

Please recommend me. Thank you very much for your help
Regards,
bupa