There are two different fields in the footprint file format. One is the at field and one is the offset field.
One of them is metric and only supported in kicad 5, one is imperial and supported by both. (but changing the footprint with v5 will convert it to the metric version if it is different to 0.)
I can not quite remember which field is for what but that should be easy for you do find out via a few experiments.