In terms of reference, it is correct to affirm that
"Over 1,700 websites..." (line 18) - refers to the number of websites visited by college students in the US.
"...11.7 terabytes..." (lines 19-20) - refers to the volume of memory used in archiving the chosen websites.
"...96 percent of the websites..." (lines 20-21) - refers to the share of websites that were eliminated by students.
"...24 percent of the websites..." (lines 22-23) - refers to the websites considered extremely relevant by educational specialists.
"...68 web collections..." (line 26) - refers to the number of sites that were included in the archive.