Since you are comparing two line charts, the range of values can be different. The system is engineered to automically scale down each axis so that the two charts can be best viewed against each other..Otherwise it will be much more difficult to compare the trends you are requesting.
So, each line chart has its own axis of values. If you look at the top of the chart, the legend shows which chart is which + the % change of each for the time period you selected.
GREEN LINE - corresponds to the LEFT side green colored axis
RED LINE - corresponds to the RIGHT side red colored axis
if you hover your mouse over each line, the exact value will display and you can look at the corresponding colored axis to confirm the number that popped up.
In this chart:
Tri/Soho/Village, 4BTH+, 5M+ Pending Sales is the green line chart that dropped 33.3% in the past 1YR. UES, 4BTH+, 5M+ Pending Sales is the red line chart and that dropped 14.3% in the past 1YR
The red line chart has a higher range because you see that in mid-May this hit 22, whereas the highest point the green line chart ever hit was 8. So the ranges on each side are scaled differently to show u the trends more clearly. If both scales were to 25, the red line chart would be hovering along the bottom and it would be hard to identify the trend difference