RPM on Cylinders 2 & 3 twice that on Cylinders 1 & 2

I have a 2003 Yamaha F90TLRB.

When doing some testing the cylinders 1 & 2 read 1300 RPM, and cylinders 2 & 3 read 3600 RPM on a digital tach/timing light.
What does this mean or indicate?

Ignition Coil 1 fires cylinders 1 and 4, while Ignition coil 2 fires cylinders 2 & 3.
The ignition coils check good (resistance values and Peak VDC input voltages are the same).
I get the same results when the coils are swapped.

I understand its a waste-spark ignition system, but the crankshaft is turning at the same speed, so how is the RPM reading different?

Re: RPM on Cylinders 3 & 4 twice that on Cylinders 1 & 2

Sorry guys.

Should have proof read my post. Title should say "RPM on Cylinders 3 & 4 twice that on Cylinders 1 & 2"

Cylinders 1 & 2 read 1300 RPM - Cylinders 3 & 4 read 3600PM with a digital tach/timing light.