If you follow correct procedure for an oil change, and if your oiling system is working correctly, you will only have somewhere between four and eight ounces of oil left in the sump. If you really think you have 32 ounces of old oil remaining in the engine after an oil change, you really should get that POS to the shop right away 'cause something is far from copacetic.
If you have a Twin Cam and want to know exactly how much oil is left in your engine, remove the casting plug in the bottom of the cases and measure what comes out. Don't do it often, that plug is not like a real drain plug and it isn't designed to be used like one. But if done carefully one time, you may be enlightened as to how little oil is really left in the sump (assuming you followed the oil change procedure). On an M8 you can remove the crank sensor from the bottom of the case and measure what comes out.
Trust me, if you take your car or truck to a fast lube joint for oil changes, in most cases they are leaving more than four ounces in your engine. They don't wait around for all the oil in the top end to drain down completely, they pull the plug and when the oil flow slows to a trickle they jam the plug back in the hole to help meet their time limit. It's one of the many reasons I still change my own fluids in all my vehicles. I take the time to be thorough, not many for-profit shops do the same. Also, unlike those shops I have never had a filter dump all my new oil out because I didn't check for and remove the old filter gasket or didn't tighten the filter properly, I've never stripped a drain plug, I've never put the wrong fluid in any of the various "holes", and I've never damaged my vehicles in any way while doing the service. Most of those fast lube places cannot honestly make the same claim. And I count the average Harley dealership oil changers in the same category as those kids in the fast lube places btw.
Jerry