Strange engine oil level readings

[mshac]

Drained all the oil out of the rear engine and changed the filter. Before draining, rear oil level read near 8 qts. Let oil drain overnight, so hopefully got every drop out I could.

I added 6.5 qts based on advice I've seen here, and experienced with other motors. Started the engine, got good oil pressure readings, it ran smooth, so I shut it down.

I checked the dipstick, and the oil was showing near 4 qts. I thought it would come up in few moments so I checked it again later, but still barely over 4 qts!

No oil has leaked out. In fact I cleaned the engine after the oil change. Its spotless. Why do I read 4 qts when I put in 6.5 qts???

Logic would say its the wrong dipstick, with incorrect markings. If that's true, then the 8 qt marking would be more like 10.5 qts - no wonder it was blowing out oil!

I caught all the old oil in a jerry can, so I could measure it if needed.

My next step is to verify the PN on the dipstick, but have any of you ever experienced anything similar?