You're right, that paragraph is a mess and there's clearly a typo in there somewhere. Trying to follow a rules as written approach doesn't really make sense, so I'm going to start by giving my best guess as to what was intended before I give what I think the literal interpretation is. Bear in mind that the first half of my answer will necessarily be opinion based and someone else might disagree, so check with your GM before using it.
It looks like the intent is that the temporary hp act as "fake healing", which goes away after a length of time (either 10 minutes or a day, my guess is that it was changed at some point during the playtest). This healing is overwritten by any true healing the target might later receive, on a one to one basis. So if you give me 10 temporary hp and then later I get healed for 6hp from a wand of cure light wounds, then I'll be left with 4 temporary hp (and 6 permanent hp). If I use the wand again and get healed by 7hp, then the remaining temporary hp will go away and I'll regain a total of 13 permanent hp.
Of course, there's nothing stopping you from using the Field Dressing on me again. I think the first sentence means it's supposed to cost you a use of a healer's kit each time you use it, but that's a minor price. Multiple uses of the ability won't stack with themselves, although you could use it multiple times and take the highest temporary hp roll. I don't think this is overpowered in the context of Path of War, though, since several disciplines have maneuvers that give healing and can be used as often as you like.
As for the rules as written, if we ignore the blatant "only only" typo, the rules are easy to understand up to the end of the second sentence - you can use the ability to give someone temporary hp, but not more than the hp they've lost. (Strictly speaking, temporary hp don't increase your hp at all so couldn't "increase a creature's hit points beyond its normal maximum", but I think we can write that inconsistency off as an obvious shorthand.) The temporary hp last for ten minutes.
The third sentence is more confusing - a creature can only "benefit from" the ability for 24 hours after you first use it on them. The only way I can see to interpret it literally is that after you first use a field bandage on a given creature, you can then never use it on them again after 24 hours have passed. Or after they've received magic healing equal to the temporary hp you gave. But until then, it doesn't interact with magic healing at all - if I'm on 15/25hp, you give me 10 temporary hp and then heal me for 9hp then I'll have 24/25 hp and still have 10thp on top of that. But if I get magically healed for one more point - ever - then I'll lose the temporary hp and can never benefit from the ability again, ever. Nonmagical healing is ok, though, provided you can pull it off within 10 minutes before the temporary hp expire.
It should be obvious, but I don't recommend trying to use this interpretation in an actual game.