Listeners hear two voices answer the same prompt, blind, and choose the person they would rather keep talking to. Scores come from the Bradley-Terry model over those comparisons; the ± is the 95% interval around each one, so two voices whose intervals overlap are not distinguishable. Open a voice to hear every prompt it answered.
The two prompts are ranked separately, because they are not the same skill: explaining a product to a customer and walking a new colleague through a task reward different voices. Overall pools the comparisons from both.
A voice needs 50 comparisons on a board before it is ranked there. Below that the interval is too wide to place it, so it is listed as unranked rather than ranked low.