The page load time is how long it takes for the web page to completely load the first instalment on your browser (this could include all cookies, trackers, social media content etc.).
Please note that some websites load web pages in instalments to prevent extensions from blocking trackers and 3rd party content. Or some 3rd Parties invite their friends to the party and who in turn are loading their cookies and trackers in the background. You can view this activity on the SpyderWeb graph. You may have noticed this when after the web page has loaded, after a few seconds it again tries to load something in the background. If “Block Tracker & 3rd Party Content” switch is on, then the Browser Controller prevents most of this activity in the background.