They hava a page explaining how the test is administered.
I like the quote from Mark Twain on the page:
"Ours is a mongrel language which started with a child's vocabulary of three hundred words, and now consists of two hundred and twenty-five thousand; the whole lot, with the exception of the original and legitimate three hundred, borrowed, stolen, smouched from every unwatched language under the sun, the spelling of each individual word of the lot locating the source of the theft and preserving the memory of the revered crime."
which long anticipated the famous quote from James D. Nicoll,
"The problem with defending the purity of the English language is that English is about as pure as a cribhouse ****. We don't just borrow words; on occasion, English has pursued other languages down alleyways to beat them unconscious and rifle their pockets for new vocabulary."
but in addition notes the chief reason for the inconsistency of English spelling.
Walt Whitman, in his essay "Slang in America", also noted this, but in a direct rather than ironic way:
"View'd freely, the English language is the accretion and growth of every dialect, race, and range of time, and is both the free and compacted composition of all. From this point of view, it stands for Language in the largest sense, and is really the greatest of studies. It involves so much; is indeed a sort of universal absorber, combiner, and conqueror. The scope of its etymologies is the scope not only of man and civilization, but the history of Nature in all departments, and of the organic Universe, brought up to date; for all are comprehended in words, and their backgrounds. This is when words become vitaliz’d, and stand for things, as they unerringly and soon come to do, in the mind that enters on their study with fitting spirit, grasp, and appreciation."
And then there's Ralph Waldo Emerson:
"I like to be beholden to the great metropolitan English speech, the sea which receives tributaries from every region under heaven."
I suppose you're a native speaker? But even then it's a good result.
Oh, yes, I'm definitely a native speaker of English. And I learned to read at home before I started school.