@Anne272
Your listing shows the minimum stay is set to 30 nights.
Or it is set by you this way or local regulations prevent the offering of Airbnb accommodation for less then 30 nights (then you are not allowed to change minimum stay to less then 30 nights).
added:
Found this: https://www.airbnb.com/help/article/2726/vancouver
It seems to me, clicking on the Vancouver.ca liink in above article, there are 2 different licenses: one for long term (30 nights +) and one for short term ?
Hope this helps.