All those who enter United States (other than permanent residents and U.S. Citizens) should download the I-94 every time you enter United States. Please download your I-94 at https://i94.cbp.dhs.gov .
I-94 is the documents that controls your lawful status in the United States. There are high chances of error and you need to verify your I-94 for accuracy upon every entry to the United States. If there are any errors, you need to contact CBP for correction.