Seemed like government math going on there!
As for oil change intervals with your engines situation, it's hard to say, as it would just be a guess. The oil filter will still get plugged up with dirt and debris, which will cause the oil filter bypass valve to open, allowing oil to still flow, but it will be bypassing the oil filter filtration media which will have unfiltered oil flowing all throughout the engine and causing accelerated engine wear.
Also, the engine is consuming a high rate of oil because the oil holes in the piston rings are in a very high temperature area and the use of conventional petroleum oil allows the oil to create sludge, gum and varnish which together gradually start to plug up the oil holes. This restricts oil flow, reducing lubrication and cooling to that high temperature area, which causes the temperatures to increase even more, exacerbating the problem even more. It's a vicious circle. This also causes the piston rings to get gummed up and stuck, so they don't do their job of sealing very well anymore, allowing the oil to get passed the piston rings, up into the combustion chamber and burned to be sent out the exhaust as blue smoke. So the petroleum oil inside the engine is being subjected to very high temperatures, causing it to not perform it's intended job. A synthetic oil naturally resists the creation of sludge, varnish and gum.
A good synthetic oil along with an engine flush can possibly help to clean out the oil holes and free up the stuck piston rings, as a quality synthetic oil is naturally very detergent.
Have you done an oil change yet, along with the oil filter?