I think that the default setting for OneDrive is to cache a copy of files locally, so that you can work on them while NOT connected to the internet. The next time you connect to the net, OneDrive will update the cloud copy from your local copy. There is a setting that lets you change this behavior.
You can find some info about it here: »
answers.microsoft.com/en ··· eaf93dd4 though the process is probably slightly different on a Mac.