Local phone storage question

As I mentioned in a previous post, which you misunderstood, the problem is several gigabytes in use on both my Android phone and tablet, not your cloud storage. Local storage. Can I just delete the 3Gb of data showing under the Box app settings? What does it think it's holding on my phone anyway? Why would it keep anything locally?

My subsequent responses to the original weren't published, so I'm making a new post in the hope of getting some help. Do you need a screenshot to understand what I'm asking? Happy to provide one if it helps to answer my question. Thanks.