Because he read the code which had that formula.By reading "phy_tempsense" and using Merlin's formula, we can match the frontend's temperature, indeed.
I also would like to know why change WL command output with a formula.
Looking into "WL" command's help, I could not find any reference to "phy_tempsense" command.
I found a similar document from DD-WRT wiki for WL command, but it didn't have information on "phy_tempsense" as well.
Unfortunately DD-WRT refereces are "not found" anymore.
Since WL comes from a proprietary Broadcom wireless LAN driver, I could not find much information about WL usage other then the help itself. Also, Broadcom's documentation seems very cryptic to me.
I guess RMerlin's formula is correct, but why?
Why did Asus use that formula? Because Broadcom does.
Why did Broadcom use that formula? Probably because they wanted better than 1C resolution, and wanted to go higher than 127.5C. So 0 means 20C (50F, cold for a chip) and 255 means 147.5C (297.5F), which is hot enough to melt some types of plastic. (A guess based on my embedded programming experience).