Thanks, so 1‱ is an harvesting importance of 0.01%? That means the chance is 1 to 10000 to harvest the next block?
Just a simple NEM newbie question: The importance is something like 1%oo. So I guess it does not mean that my importance is 1% because my stake is much to low for such an high importance

What does it mean instead? 0,001%?
‱ are
basis points (
http://en.wikipedia.org/wiki/Basis_point). They mean per ten thousand (one hundredth of a percentage point)

Yes, 1 in 10,000 is the theoretical probability (there are other factors involved too, though). However, you should remember that only people currently harvesting are able to harvest blocks, so it is in actuality much more likely that you will harvest a block, because not everyone is harvesting on the network 24/7. With 1440 blocks a day (look at that 60s avg!
http://nembex.nem.ninja/#stats), you will likely harvest a block one or two days, would be my
guess. Please try it and report back on your experience
