Unwated Smart Scan on Bootup

Windows 7

AVG AntiVirus Free 25.8.10387a

In [Setup > Settings > Basic Protection > Smart Scan], I uncheck the checkbox for “Augo-continue Smart Scan’ and set “Frequency” to “Run manually”. Nevertheless, smart scan sometimes starts when I bootup my PC. If I do not want a scan at that moment, this consumes too much resource. Why is this happening?