According to the help for the JustField() function in DAL:
"You must define the X-coordinate parameter when using the justification character. If you omit the X-coordinate the system runs as if the justification character was not specified."
Therefore you second parameter 0 would be the problem.
However, your next question is: "You mean I have to go figure out the exact FAP point where I want the alignment? What a pain!".
You could actually employ the FieldX() function to help you in that regards. If you make sure that your fields are aligned on the left edge, then you could add a fixed amount to that value and know that all your content aligns on the decimal accordingly.
Now, your format is pretty large, so let's assume that means about 2 inches of space is needed. That would be 4800 FAP units.
The script then would do something like this:
#pos = FieldX("fieldName1") + 4800
JUSTFIELD("R", #pos, ".","fieldName1")
JUSTFIELD("R", #pos, ".","fieldName2")
JUSTFIELD("R", #pos, ".","fieldName3")
Since all your fields in this sequence should have the same left coordinate, you do not have to recalculate #pos but can instead reuse the same value for each one.