the default currency price is wrong

Hi Team,
I just set up two currency on my page, default is Thai Baht, and 2nd currency is Taiwan dollar, so i put Thai baht is rate 1, and Taiwan dollar is rate 0.84 0.01 exchage fee, but don’t know why all of my product price is change on Thai baht, it become more less,,For example, the car price is 680THB, it became to 571THB, and for NT is 0.84x 571THB = 479NT, May you let me know which part i set up wrong?
Now I already close the plugin, as all the product price is wrong, so we have to stop plugin till I figure out, thank you.