...

With multiple inputs or value categories decision table can get very large in size. Decision tables that are to too large in size are not easy to oversee and by that to understand. In general you can state that a table should have a maximum of 12 columns. When the number of columns exceeds this number it is advised to split up the table. 

...

Splitting up a decision table can be done by using sub decisions and sub decisions can be created by adding an extra attribute.

Order in a decision table

...