Distillation Curve

I have calculated distillation curve using these methods for my petro components D1160 volume basis, D2887 Wt basis, D86 Volume basis and True boiling point curve. The curves are not monotonic, the temperature for 25%, 30%, 35%, 40%, 45%, 50% are less than the temperature of 20% vaporization.

The results: 0% - 8.9K, 5%=66.79K, 10%=194K, 15%=269K, 20%=281K, 25%=254K, 30%=215K ...

Is this correct? If not where can i get correct results, can you suggest some material where can i find some correlation to predict correctly.

Thanks.