Basically you have gutter to gutter oil the entire length of the pattern. By USBC rule oil must be distributed from edge board to edge board for the entire distance that oil is applied and there must be at least 3 units (3 units is like nothing) where ever oil is applied.
So your 42' pattern will have some amount of oil gutter to gutter.
past 42' the lane should be dry, no oil anywhere.
Now there will be varying amounts of oil in the different areas oil is applied. You'll have the most oil in the middle( usually 10to10) with it tapering off going toward the gutters (10 to 1). This is what the ratio (like a 10:1 ratio) is referring to, the amount of oil 10to10 vs 10to1.
Okay here's a example of 42' house pattern, on the left where ever you see blue is where there is oil:
Take a look at this video:
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