When looking at transactions in a tangle explorer website, some transactions like this (not mine) show up as Weight Magnitude 16.
This also happens for my transactions where I am sure that I had set Weight Magnitude 14.
Did I do more PoW than needed? Is this a bug, or why does this happen?
When you perform PoW, you specify "Min Weight Magnitude" (not Weight Magnitude). That means that the PoW will modify your transaction hash until it ends (in ternary) with at least 14 zeroes.
As the hashing is random, it can happen that your hash ends with more zeroes (without you doing extra work), thus resulting in a transaction with Weight Magnitude of 16 instead of 14. This is not a problem and everything works as intended.
(Compare it to for example if you play the Lottery until you win 1000, it might happen that you win a million before you win 1000).
