The Content Timeframe filter appears in the Content Filter section as soon as a Full Text Search or Brand Mentions filter is active. It limits the content that is considered to posts published within the selected period: the last 7, 30 or 90 days, or the last 6 or 12 months. "All" considers every indexed post regardless of age.
The timeframe applies to the upload date of the content, not to the creator profile. A creator therefore only matches if they posted about your keyword or mentioned the brand within the chosen window — a great way to distinguish currently active cooperations from old ones. Shorter windows also speed up orientation around seasonal topics and trends.