Router Security Log Shows Many Blocked TCP Connections

When checking my router tonight I looked at its security log. I saw thousands of blocked tcp traffic. Why are these considered security events? The log shows many blocked tcp incoming request from many different ips and on different ports. Here is one example below: TCP Blocked Connection On Security Log

Does a log fill up with thousands of blocked tcp events like this through normal internet surfing or is this something to be more concerned about? Or does this just mean the router’s firewall is just doing its job and logs every time it receives tcp traffic inbound that I did not initiate?

(As a side note I did find UPnP was on and Wifi Protected Setup was on too by default, so I turned those off)