You can't change that date range, as it's a representation of what is currently IN the database. I.e. for some reason nothing older than the 15th is in your logs. I assume based on the settings you have in your screenshot, that now it'll say something to the effect of 10/15/2018 - 10/29/2018 ?
Unless something is wrong, or you maybe changed settings (unchecked boxes, etc..) prior to the screenshot, i'd expect the 14 days of logs as of today.
Brian