You have to evaluate the equasion you are using for the setting of the numer of series

```
// Stack the data
Data Table( "Sample_data2" ) << Stack(
columns( ColList ),
Source Label Column( "Label" ),
Stacked Data Column( "Data" ),
Number of Series(eval( j/12 ) ),
Contiguous
);
```

The resulting value has to be an integer, which means your value of the variable "j" has to be, 12, 24, 36 etc

Jim