Don't  worry bro. its all good. You dont have to call them back, they are simply trying to help you out. When u filed tax you claimed  that u didnt earn any amount last year, but had paid certain amount towards tuition. Thats make you eligible to get certain benefits that you have described above, because you fall under poverty line. Since, u fall under the poverty line, they just trying to help u out with the benefits program by sending the courtesy letter and letting you know that ur eligible for those benefits..

TAKE A CHILL PILL BRO AND DONT GET TENSED..