Don't worry @Richard R it's only a test with its flaws. I mean that if you do it again as you know how it is working I'm sure you'll score much higher.
For me, as others said, most of the singing was out of tune in itself; the melodic discrimination is a bit weird too as, for instance, if you're accustomed to Indian music, there was nothing really odd, but as it's related to European conception of music some oddities are obvious in our fixed musical system. For the beat, if you take classical music, the notion of beat is not as accurate as modern light music, but linked to the perception of time of the orchestra leader.
And, as they mention it, your score is linked to the participants average score and most of the participants are already into music, so it's totally biased.
Those IQ tests are absolutely not reliable, but can give you some hints to improve.
Keep on playing as I'm sure you're a really good bassist.