Effectiveness of HU on ET w/MPL?

I was diagnosed with ET & MPL 2 months ago, platelet count of 850 and the doctor started me on HU 500mg, 3 pills a week (M, W, F). After one month, platelet count was 716, so he increased dosage to 7 pills a week (one each day). Two weeks later, platelet count was 699, so he increased dosage to 11 pills a week (two each day, except M/W/F with only one). Three weeks later, platelet count was 675, so he increased dosage to 14 pills a week (two each day). That brings us to the present. So, after two months altogether from the start of the diagnosis, platelet count went from 850 to 675. I became discouraged as I thought HU would bring the platelet count lower and faster. It is going in the right direction but it is still high.What realistically should my expectations be? What is everyone else's experience in terms of the amount of time it took to get the count to less than 400? Would appreciate some feedback on this. Thanks!