The website appears to describe an early release of the DES DR1 used internally, not the final set of tables released from DES. We will correct this promptly.
To answer your question, the exposure information released is in the 'img2coadd' table that lists each exposure that contributed to a specific tile. That exposure number can be related to information stored in the archive or to tables under the 'ivoa' schema used to serve image data (write back with what you're trying to do if you need more details).