Understanding URL options

How can I understand the ranking on TechEM? For instance, the main page (round 16, 6/6/2018) has the top two listings as h2o and ulib-postgres. However, the link I got from another page has the top two listings as urweb and revenj-jvm. I was a confused at first, then notice the &c=6 in the URL. I am no web person. Can someone explain it to me? Thanks.