we all know (??) that G4 is the gcode for dwell
it takes a parameter to indicate the dwell (pause) duration

I have seen various ways of expressing this
I asked in another forum and wasn't entirly happy with the answers
they included - "you can specify seconds or milliseconds"!!

so:
G4 X123 // dwell for 123 seconds or 123 milliseconds?
G4 X123.0 // dwell for 123 seconds or 123 milliseconds?
G4 P123 // dwell for 123 seconds or 123 milliseconds?
G4 P123.0 // dwell for 123 seconds or 123 milliseconds?
which is right?

actually what I really want to know is how to decode the dwell command
(I'm working on a gcode interpreter for an Arduino based controller)