Quoting Patrick Gundlach :

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in \setupcolumns, what is ntop=<number>

From the source: the minimum number op balanced top lines

Consider \starttext \startcolumns[n=2,ntop=15,balance=yes] \dorecurse{20}{This is a test line to check for balancing. } \stopcolumns \page \startcolumns[n=2,ntop=5,balance=yes] \dorecurse{20}{This is a test line to check for balancing. } \stopcolumns \stoptext

This seems to be a binary switch, right? no difference in your example between ntop=15 and ntop=13.

Yes. The way I understand this is: if the number of lines in the column after balancing are greater than ntop, do column balancing (if enabled) otherwise not. For example, \showgrid \starttext \dostepwiserecurse{5}{15}{1}{ \section{\recurselevel} \startcolumns[n=2,ntop=\recurselevel,balance=yes] \dorecurse{20}{This is a test line to check for balancing. } \stopcolumns \page} \stoptext Aditya