In the Price History, the Historical Low should represent what is displayed by the Price History Zoom level.
If the the zoom level is one year, the historical low should display prices only for the year selected. If the zoom slider is moved further back in time (i.e. to the left), then the historical low will update to reflect the historical low for the time period covered (even if a lower price occurred outside of the selected time period).
The absolute historical low (the all-time low) should always be displayed at the top of the page.
The reasoning behind this is that some historical lows occurred so far in the past they are no longer relevant. It also gives the ability to filter out those one-off freebies that once happened and have never since happened.