Here they say: 'How is it that he who blows like one only, should be called one and a half (adhyardha)?' And the answer is: 'Because, when the wind was blowing, everything grew (adhyardhnot).' He asked: 'Who is the one god?' Yagnavalkya replied: 'Breath (prana), and he is Brahman (the Sutratman), and they call him That (tyad).'

In plain words: People ask why the wind, which is one, is called "one and a half." The answer is a word-play: when the wind blows, everything grows. Finally Yagnavalkya says the one god is breath, which is Brahman, the thread running through all things, and people simply call it "That."