Thanks for testing the tool. We fixed the computation for the case of a single chromosome abnormality.
The tool follows the definitions in Dr. Greenberg's original article:
International Scoring System for Evaluating Prognosis in Myelodysplastic Syndromes, Blood, Vol 89 No 6, 1997, which defines the karyotype categories as follows:
Good, normal, -Y, del(5q), del(20q); Poor, complex (>=3 abnormalities) or chromosome 7 anomalies; Intermediate, other abnormalities.
Trisomy 8 is not itemized, so it falls into the "other abnormalities" category under the IPSS. The newer IPSS-R system specifically itemizes trisomy 8.