This is mostly in the mindset of how cum shoots out in short, quick successions. The word substitutes "jac" in ejaculation with "fart."
Amy: "Fred, you efartulated in your sleep last night. It was gross!"
Fred: "It was those beans you fixed last night, dear. They give me so much gas, it gave me an efartulation!"
A complex portmanteau word. "Exactly" + "Accurately" = "Exactulately". Not just exact, not just accurate - but both.
Possibly (er, exactulately) derived from a brief verbal stumble in a youtube video on the Tested Channel about "Inside Adam Savage's Cave: Model Making for Movies".