Each industry is represented by a series of 3 connected dots. The middle dot is the median wage for that sector and the top and bottom dots are the averages for high and low earners (90th and 10th percentile). This shows some industries have a huge difference between top earners and what most others are paid.
The height of the dots reflects the hourly wage in HK$. The industry, or green line/dots, is also placed left to right along the x axis according to how many people work in that industry. You can see Import and Export Trade alone out to the right of the chart. By far the biggest employment sector in Hong Kong.
Restaurants and estate services had the lowest two averages.