Yep! Or maybe even measure this as 0.01265 light-years to appreciate the size, because 800 AU is massive. Pluto’s semimajor axis is less than 40 AU.

AU is NOT used to measure size. It is used to measure distance. 1 AU = the distance of the Earth from the sun (93 million miles). This is not size. It is a distance. It's the same concept why we use different measuring standards. If measuring the length of you table, you use inches. If measuring how far you throw a football, you use yards. If measuring how far you drive, you use miles. AU is just a measurement standard. It makes taking about large distances easier without the numbers being too large to be hard to use and conceptualize. If I drove from one city to another, which is 320 miles away, what if I gave you that distance in inches? It's a huge number and difficult to deal with. After AU, the standard we use is light years.