What exactly was in the bags, just water or was there something in the water? I've not come across any of my local shops selling things like that.
If they are selling water from tanks with cycled filters that will do virtually nothing to help cycle a new filter. There are very very few of the filter bacteria free in water. They grow in the biofilm which is tightly bound to sufaces. This is how we can wash the filter media without losing the bacteria. The only reason we have to use old tank water to do the washing is that chlorine or chloramine in tapwater will kill the bacteria.
If there was something in the bags, it could well be mature media from their filtration system. This would be very useful as it is a guaranteed way of speeding up a cycle, unless it had been left in the bags too long. Maybe that's why there were only a few bags so they'd get sold before the bacteria in them died off.
I would go back to the shop or ring them and ask them what's in the bags. If it is mature media, get some straight away, bring it home asap and put it in your filter. Replace the carbon sponge with it
So long as mature media is treated like a fish, ie kept in water with an air supply, it will seed your filter cutting down cycling time considerably. In fact, with enough mature media it is possible to instantly cycle a tank - this is what I do when setting up a quarantine tank for newly purchased fish, I steal some media from one of my mature tanks. I wouldn't risk that with purchased media though, just in case it's been in the bag a while. But it could see your filter cycled in a few days rather than weeks. But you would need to leave any mature media in the filter for a month or so after the filter cycled to make sure enough bacteria had grown in the rest of the media.