Everybody's body is different. You lost the first 20 in a little more than a month, so 15 pounds by the end of June sounds doable. Another 20 by mid-august - maybe?
If you stay 100% on program, this is not unreasonable.
BUTBUTBUT don't be upset if you don't hit your schedule. Be happy about your progress no matter how fast or slow it goes. Every pound is a victory.
I made myself a little spreadsheet when I started. It had dates on one side, and columns for 2 pounds a week, 3 pounds a week, etc. I think I went up to 5 in the spreadsheet, but I never lost that fast. This way I could see what weight I would be by when if I kept losing at that rate. It kept me focused and motivated, but in reality, it never went as fast as I wanted it to.
I still got there. Just took me longer than I expected.