In Graph Builder, users do not need to drag a value onto the y-axis in order to create a bar graph.
Without specifying a Y value, JMP will count -- or calculate an aggregate value.
Which one? For some of the settings, this depends on the version of JMP being used.
comparison JMP18 vs. JMP19:

Names Default to Here(1);
dt = Open( "$SAMPLE_DATA/Big Class Families.jmp" );
Graph Builder(
Variables( X( :sex ), Overlay( :age ) ),
Elements( Bar( X, Legend( 3 ), Summary Statistic( "Median" ) ) )
);
Median is great to get rid of outliers, so maybe use it as a default setting in the preferences?
Think twice - and decide whether you would prefer meaningful results for 'values' or for 'counts'.
