why page speed Grade is smaller Although page load time is grater?

Hi, I'm trying to increase speed of a website I test it with http://gtmetrix.com/ and the result was: Page Speed Grade: (82%) YSlow Grade: (72%) Page load time: 6.31s Total page size: 0.95MB Total number of requests: 51 also you can see the result in this link http://generalsite.ir/untitled2.png at the bottom of site theres a link that when click I show google map in a popup window. I removed it to increase page speed and retest the site the result was this Page Speed Grade: (70%) YSlow Grade: (76%) Page load time: 0.91s Total page size: 501KB Total number of requests: 17
also you can see the result in link below http://generalsite.ir/untitled.png I wonder why page speed Grade is smaller than first test Although page load time is grater than (and Total number of ...