You may be behind a transparent proxy, or have a user-agent string not in P0f tool database. Vardump: notice that you get almost the same uptime for your Mac a

You may be behind a transparent proxy, or have a user-agent string not in P0f tool database. Vardump: notice that you get almost the same uptime for your Mac and your Windows PC: 19 days 18 hrs 10 min. It appears your router (NAT) is handling / modifying the tcp/ip timestamp. Btw, even if the timestamp is wrong, it can provide some entropy (=measure of uniqueness compared to other users).