Spec here is about consistency leaving factory. In fact, MM factory spec for most pickups on most electric guitars is easily remembered as "6, 5, 4", meaning 6/32" for the bass pickup, 5/32" for the middle pickup, and 4/32" for the bridge pickup. That's measured from the bottom of the open strings to the top of pickup pole piece and a perhaps a little closer on the high string side.
For the other 205 countries of the world that's 4.75 mm, 4.0 mm, and 3.0 mm, neck, middle, bridge.
But factory spec is not a goal, it's more of a suggestion. Close your eyes and let your ears decide. Example, my Silhouette Special is currently "7, 6, 5 1/2". But that can change weekly too. I frequently grab a screwdriver and make adjustments as I feel the want.