found some Codefree strips so side by side...
07:20
Bayer 4.0
Codefree 5.0
2nd test
Bayer 4.2
Codefree 4.8
Been testing with Bayer for a couple of years.
When I changed over I found there to be a steady 0.5 difference.
Stick to one and watch the trends, rather than the actual values is my moto.