Ores and oil wells never decrease or deplete. Miners show a strange 'expected resources', due to what I consider a bug in Factorio; see https://forums.factorio.com/viewtopic.php?f=7&t=41720 ; This does not seem to be fixable by a mod. When hovering over ore, '723%' means 723 ore. The X/s expected resources when hovering over miners is mostly meaningless; the number X is actually OreCount*((MiningSpeed-MiningHardness)*MiningSpeed/MiningTime)/100, the result of which has no meaning.