Not sure where that formula came from, but I'm saying dealing with NHRA in Como eliminator and some CID restricted circle jerk stuff, that won't fly. You are off enough to not fit the rules.
Bore X Bore X Stroke X .7854 X the number of cylinders. Right out of the NHRA rule book.
I've seen guys get burned by this before and it's not fun to watch someone lose a race of even a National Record because the math isn't correct.
So here is your math.
4.030 X 4.030 X 3.79 X .7854 = 48.343734 X 8 = 386.74987
That means you engine is 387 inches. I usually go out one more digit on the bore. But ghats close enough for this.
4 cubic inches over what you think is a big deal for the powers that be and write the rules.
In your case, it's just semantics, but everyone should know the actual simple formula to calculate CID so you know what you have.