At first I wondered whether the test adjusts either direction for lack-of-patience; and then I realized I could run an experiment.

There don't appear to be any points granted for finishing early; I just took the test three times, guessing randomly as fast as possible, and scored 93 first then <79 (what appears to be the lowest score possible) twice and 93 the third time, and then took the test a fourth time, guessing randomly at a rate of 1 question/minute (finishing with 1 minute to spare), and got 83. This appears to reject the hypothesis that finishing early boosts your score (or, inversely, taking more time lowers your score).

Though... V whfg ernyvmrq vg qbrfa'g nccrne gb inel gur cbfvgvba bs gur nafjref ba frcnengr nggrzcgf, fb n zber gubebhtu grfg jbhyq hfr n cerqrgrezvarq frdhrapr bs nafjref gung fbzrgvzrf erfhyg va na VD nobir 79, naq inel gur gvzr gb pbzcyrgr gur grfg hfvat gung frdhrapr. ... but I have to get to bed soon so I'm not going to spend another 40 minutes to run that test.