It seems the wrong show in Visits by Days Since Last Visit. beacuse in 365+ days, i did not put tracking code in website, but 365+ days show a value.
This is a calculated value based on the data sent with the tracking request.
Within such a tracking request a timestamp of the last visit is sent. This value is based on a cookie. So theoretically this value can be faked by changing the cookie or send old timestamps with the tracking request.
@SteveG thanks your reply. but how do I fix the issue?