301 HP actually nearly maximizes life orb recoil. on paper, life orb deals 10% max hp recoil, but since the pokemon engine rounds damage down, the actual percentage varies a little. so, what people mean when they say "minimize life orb recoil" is "minimize the ratio of life orb recoil damage to maximum hp".
if you have 301 HP, you lose 30 HP from LO recoil, so the ratio is 30/301 = 0.09966777. if you have 302 HP, you lose the same amount of HP from recoil, but your max HP is higher - therefore, the ratio is lower so 302 HP takes "less" recoil damage than 301 HP. this happens all the way until you get to 309 HP since you're increasing the denominator but not touching the numerator. if you go down to 300 HP, you take the same amount of recoil, but your max HP is lowered, so you take "more" recoil damage.
therefore, if your HP is ABx, where A and B are single-digit integers and x is a variable from 0-9, for any fixed A and B a given pokemon takes the "least" recoil damage when x is 9 (such as 309) and the "most" recoil damage when x is 0 (such as 300). you probably want to aim for 299 (32 EVs) or 309 (72 EVs) on this set to minimize LO.
another way of thinking about this if you don't want to use ratios is to just imagine how much HP the pokemon has left after attacking X number of times.
with 301 HP, it loses 30 HP per turn, so after (X) number of attacks its HP is: (1) 271; (2) 241; (3) 211; (4) 181; ...
with 299 HP, it loses 29 HP per turn, so after (Y) number of attacks its HP is: (1) 270; (2) 241; (3) 212; (4) 183; ... so you can see while this set starts off with less HP, it regains the "lost" HP very quickly, and soon has more HP than the set that started off with the most HP.
this was kinda long but hopefully you understand LO recoil numbers better now!
