From what you've said, it seems you have this:
                                  
                   P              H                                         
            -------●--------------●---
            -4 -3 -2 -1  0  1  2  3  4  

You could rename the point H as Q where H is at 3 and then the 
distance from P to Q would be 5 units, and the segment PQ would 
be 5. Like this:

                   P              Q                                         
            -------●--------------●---
            -4 -3 -2 -1  0  1  2  3  4


Or you could extend the number line on the left and put Q at -7 
and then the distance from P to Q would be 5, and the segment PQ 
would be 5.
Like this:
                                  
    Q              P              H 
    ●--------------●--------------●---
   -7 -6 -5 -4 -3 -2 -1  0  1  2  3  4 

Edwin