Don't even worry about all those numeric figures, just ride the bike. You'll find, after a few weeks, that certain gear combinations work best in certain situations, so you end up using them. Other combinations provide no advantage, so you ignore them. Period.
The closest I've ever bothered to worry about gear combinations and ratios is finding a comfortable combination for large chainring/middle freewheel cog while keeping my normal cadence on a flat road (leaving me a couple of cogs for fast downhill pedaling). Which gives me a speed of about 16mph in a normal, relaxed riding mode. Which keeps me happy. This got me to change all my large chainrings to 48t or 49t (depending on availability) from the original 52t. Other than that, I could care less. I'm too busy riding.
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Syke
“No one in this world, so far as I know — and I have searched the records for years, and employed agents to help me — has ever lost money by underestimating the intelligence of the great masses of the plain people. Nor has anyone ever lost public office thereby.”
H.L. Mencken, (1926)