Ah yes, life was simpler before calculators. I still have my engineering slide rule

from back in the day when 1 or 2 digits and a power of 10 was sufficient for a lot of things and 3 digits was a stretch. My neighbor in the concrete business lamented customers with their plotted plans that expect concrete poured to quarter-inch tolerances when the forms will bow more than that.
Even now, most people I run into want things in relatable, ballpark terms like 750 or 800, not 776. The details usually come out only when comparing detailed specifications, and most of the time there really isn't a significant difference.
I treat all focal lengths and f-stops as "around x". Life is easier this way.