Hello John,
Yes, it happens because your test contains only 302 words (the English wordlist size), which is typed in about 2 minutes if your speed is around 150 WPM.
When choosing a pre-set duration (2, 5 or 10 minutes), the size of the test (ie the number of words to be typed) automatically increases:
2 minutes = 2 x 302 words (604)
5 minutes = 4 x 302 words (1208)
10 minutes = 8 x 302 words (2416)
But if you manually set a different duration, the test will be 302 words long by default. So if you want to type for 9 or 11 minutes, for example, you won't have enough words.
To solve this problem, you have to manually change the size of the wordlist too. When inspecting element, look for the following line:
Then increase the number of words by copying the list X times (between 30 and 40 times should be enough for 1-hour typing).
Don't forget the "|" between each duplicate list and don't put a "|" after the last word.
I've never tested this duration, but I think it should work with this method.
Good luck!