The GetProcessCapabilityRecord will return the SPCProcessCapabilityRecord at a given index. You can then look at the CalculationType property.
Something like this should work:
for (int i = 0; i < ChartData.NumProcessCapabilityValues; i++)
{
SPCProcessCapabilityRecord pc = ChartData.GetProcessCapabilityRecord(i);
int pctype = pc.CalculationType;
}