I-539 to F1 in TX center

I filed I-539 to TX center to change from H1 to F1. I got the receipt on May, 17th and it says it will take about 140-200 days. I am kind of worried that it will delay my enrollmant to the graduate school this august. But the international office told me that it only take up to 2 month in TX cneter. I checked the processing date on TX center's website. It does not chage for long time. (Mar,22nd currnetly)> anyboday have such experience recently? Really appreciate for sharing the information.