BUTLER CREEK30200 Objective cover

Why does the pda recommend a 20 cover (43.2 mm diameter) for my scope (zeiss conquest 3-10x50mm), even though it says the eye outer diam is 45 mm?

Scope eyepiece is 1.68 inches. should i get the cap that is 1.675 or 1.700 inches? in other words, should i go bigger or smaller?

What size do i need for the nikon prostaff 3-9 x 50 (nikoplex)

I currently have the Nikon ProStaff Rimfire 4 x 32 Black Matte Riflescope, what size caps am I supposed to purchase? The chart does not match info.