Private IP 10.0.0.0/8 found from ISP when doing traceroute once leaving local (private) network

I just started working for a major enterprise in northern Washington, and when it comes to networking, I am what you would call "wet behind the ears." We are experiencing some weird latency/timeouts/packet loss from our edge router to the first hop to the ISP which shows up as a 10.x.x.x.... I know that 10.0.0.0/8 is a class A non-routable subnet, so how is it that the ISP can have that private IP scheme on the internet?