a mil other places might be short for millimeter but a mil in the shooting community as far back in the military as i can remember has always been short for miliradian...which is also called mrad by some other people and manufactures. So as far as jargon is concerned...they are usually synonymous.
however this, is unnecessarily complicated. When talking about inches yes. in the formula when doing a range est with mils, the easy way is to round off 27.77 to 27.78. As to figure out what the mill angle is at that distance...the rounded number is going to be a fraction difference. .027. So + .03 mils difference by rounding the .7777778 to any form of 28"
This has no real functionality though unless you are just trying to figure out the scope adjustments when bzoing at a closer range. so 1.00003ish inches.
27.78/1000