You mark the stock springs left and right, then put the new taller coils onto the side that had the taller coil. Then there is no confusion.
Lame answer for a vendor. You're assuming the previous springs were positioned properly to begin with springs never been previously messed with.
This has been a problem from day one (30+years) with both Dobinson and ARB.
If the manufacture would be smart enough to change their labels this would not be a problem.
i.e.
RHD - DRIVERSIDE. or LHD - DRIVERSIDE
LHD - PASSENGER or RHD - PASSENGER