Rating: 3 / 5
Results of some web research: one Potable Aqua tablet in a liter of water generates 8 mg/l or 8ppm iodine, which does the work.
Ignoring cryptosporodium: in clear, warm water the nasties are gone in less than 10 mins. If the water is not so warm or not so clear, wait 20-30 mins. In the worst case you can use two tablets to get 16 mg/l and wait 20-30 mins...this is what the bottle says. The manufacturer figures they won't get sued if they always assume the worst case, and of course they sell more that way.
Make sure the water container is sealed after treatment, as the iodine can evaporate into the air. Another reason the manufacturer recommends double the standard dose.
Finally, if you use a whopping 32 mg/l, or four tablets per liter, you can kill everything really fast, in minutes, but who could stand the taste!
As with all chemical treatments, what is important is the dose times the contact time. I.e. you can e.g. halve the dose and double the contact time to get the same effect. But don't take this too far as other effects come into play with long contact times (evaporation of active ingredient; interaction with container or impurities; UV deactivation of the active ingredient, particularly for ClO2, etc).