There are four possible lengths of the starting remainder bar, and each item consistently uses the same one. So, if you're at Iron Lake, and you start mining, and the remainder bar is at placement B, then you know that you're about to dig up some cobalt ore.
The second consistent input for each item is the strike zone. Logging uses five zones, and mining and fishing use four (there are other theories, but if you follow these you'll be very solid). The images show good places to strike to hit each zone. Cobalt ore's strike zone is 4. So, if you're mining at Iron Lake, and the remainder bar is at placement B, then you know that you merely need to strike at zone 4 to dig up your cobalt ore.
If you forget which zone is which, or which remainder bar is which, you can always mouse over the relevant cell to show a popup image. Also, when you're at a camp, pull up that camp's page, and pay special heed to the Remainder Bar column. Ideally using this chart will let you know what you will dig up/chop down/fish up before you even strike.
Note: In order for the strike zone to be consistent, you must be high enough level and have adequate amounts in the appropriate stat (Botany STR, Mining VIT, Fishing DEX). When you don't meet these requirements, the item may be placed into a random zone.
Lastly, thanks goes out to Aviha Chai from Balmung for gathering all the remainders, strike zones, and max yields for every logged/mined/quarried/harvested item in the game! Fishing data gathered by Aviha Chai and Aleczan Knighthill (Excalibur).
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