             min     : 0
             max     : @length - 1
             step    : 1
-            values  : [Math.max(@revision_num - 10, 0), @revision_num]
+            values  : [Math.max(Math.floor(@revision_num/2), 0), @revision_num]
             range   : true
             slide  : (event, ui) => # TODO: debounce this
                 set_doc(@goto_diff(ui.values[0], ui.values[1]))

            @element.find(".salvus-editor-history-diff-mode").show()
            @diff_slider.show()
            @slider.hide()
        else
            @element.find("a[href=#hide-diff]").hide()
            @element.find("a[href=#show-diff]").show()
            @element.find(".salvus-editor-history-diff-mode").hide()
            @diff_slider.hide()
            @slider.show()

    set_doc: (time) =>
        if not time?

        if not num2?
            return
        if not num1?
            num1 = @revision_num1 ? Math.max(0, Math.floor(num2/2))
        versions = @syncstring.all_versions()
        if not versions?
            # not yet initialized
