As you're able to draw outside of the array you're obviously able to tabwrite outside it. To help yourself in this case I would limit the input to the [tabwrite] object. [moses] does that trick. If you set the argument to 20 every number up to 20 goes to the left outlet, 20 and above to the right one, so you're not going to use that outlet.
 
/numberbox] (ctrl/cmd 3) (or whatever input of floats)
|
[moses 20]
|
[tabwrite your_array]