Get 40% discount on part of the energy rental fee!

Hi guys, I just found a new way to take advantage of the energy rental platform. When returning rented energy on the JustLend energy rental platform, there is a 40% around discount on part of the energy rental fee!!!
official doc: Energy Rental Market | JustLend DAO Docs

After several tests, it was discovered that if you already have some energy on your account and rent an additional energy, upon normal return, the rental fee of paid will be discounted by 40% around. The next is my steps,

We can find the net expenditure amount = 293.126 - 290.421 = 2.705 TRX.

Energy is restored from 59k to 118k, with a net recovery of 59k energy, which is equivalent to a unit price of 2.705 TRX / 59k = 2705000 Sun / 59k = 45.8 Sun, which is 38% cheaper than the rental price of 74 Sun.