Okay, there is bit confusion there and so I explain.<br/><br/>Firstly the two fort saves are needed to resist two different effects. Other effect is called nauseating, if you fail roll vs that, you can take only single move action for 1 round. All swarms have this special attack in common.<br/><br/>Second fort save is to resist against poison (spider bite is poisonous, with rat swarm you would roll against disease). The poison damage is 1d3 to strength, not to HP.<br/><br/>Now, to further explain let's use example. A barbarian Conan gets bitten by nasty spider, normally man of virtue of physical fortitude he rolls nat 1 and so he fails against spider's pitiful poison save DC (which is 11). He has strength 20 and thus spider rolls with 1d3 a two, so Conan looses -2pts strength and thus has strength 18 until he recovers from poison.<br/><br/>He needs roll save again one minute later as poison takes hit on you twice (if you fail first fort save). Let's assume Conan succeed but if he had failed second save, the spider would had rolled 1d3 a second time and added the damage top of what Conan had already suffered. So if spider had been lucky (or Conan unlucky this case in his fort saves), Conan may had lost six points of strength just because of poison.<br/><br/>Now, to recover from stat damage your char needs rest for one day in bed to get 1 point back. A full day in bed rest would recover two points. If the stat loss is drain instead damage, it means you loose permanently the stat points lost with said attack. But the spiders do not cause such damage, so any strength loss can be recovered by resting.<br/><br/>Spiders can do 1d6 damage per round (to HP), so unless Jazerat has horrible luck (with dice) he should survive.<br/><br/>Edit; Aye, Snake nailed reason for two fort saves with poison. If first roll succeeds, you did not get affected by poison that round (nor 1 minute later). But if you fail, the poison gets in your system and thus haves initial damage and then your body needs resist the secondary effect of the poison.