In a game manual, there is a description of a rare item that sometimes appears instead of a regular one. The rule determining when this rare item appears is this:
16回に1度、Xのかわりに出現。
In an earlier question concerning the same sentence I got quite a lot of answers with translation. Every answer translates the condition as
Once every 16 times
However I am still not sure whether this means:
- There is a probability of 1/16 that a rare item appears.
- The rare item appears every 16th time.
Which one is correct? And, how to express the second one in Japanese?