You may also use the operator form of Merge which compacts the Dataset query a bit.
Merge
Dataset
myds[Merge[Min], {"Reinsurance Payment Amount (or Not Eligible)", "Individual Market Risk Adjustment Transfer Amount"}]
Hope this helps.
I wish someone could explain to me why your original construction with Min[] did not work. My only guess is that it is related to the difference between these:
Min[]
Options[Min] Options[Total]
The second one gives Method -> Automatic. I cannot see how this matters. But I can hope for (eventual) enlightenment.
Method -> Automatic
A more compact construct as given by in the documentation of Dataset is:
myds[Total, {"Reinsurance Payment Amount (or Not Eligible)", "Individual Market Risk Adjustment Transfer Amount", "Small Group Risk Adjustment Transfer Amount"}]
