Scrape Sensor on SDG&E's Website

I am trying to scrape my gas usage from the SDG&E website, but I can’t get it to work. I went to the website and copied the selector for my gas usage for today, and it is

#highcharts-wjl6sw7-72 > div > span > span:nth-child(3),

but putting that into the “select” part of the Scrape sensor doesn’t work. The full XPath is

/html/body/div[4]/div[2]/div[1]/div/div[2]/div/div[1]/div/div[2]/div/div[2]/div[1]/div[2]/div/div/span/span[2]

but I don’t know how to translate that into a CSS selector for the Scrape sensor. I also don’t know what to put for the Attribute or Index options either… All I want is to scrape my daily gas usage from the website but my sensor is coming up as “unknown.” Any ideas?

Thanks!