What is it trying to say for my pool?

According to this, you can go swimming just as soon as you dissolve this Instant Pool Water Conditioner stuff into the pool. The "acidic and 4 to 7 days" thing was the manufacturer of the Instant stuff saying how their Instant Conditioner is better than cyanuric acid which they say takes very long to dissolve and being an acid can be a bit dangerous. The pH of this Instant stuff is only 8.0 which is very close to neutral pH so it should be OK to go swimming very soon after adding the Instant Conditioner and waiting for it to dissolve which it says it does, well, instantly! Do be careful about going in if ANY other chemicals like chlorine or algicides have been also added to the pool very recently, and TEST the pH of the water to make sure it's in the acceptable range before going in. Enjoy your pool!