The Big Four Train

I am new to this forum and I was wondering if someone could answer a question regarding the “Big Four”. I am researching my family tree and my ggg-grandfather was hit by train No. 50 on the Big Four. What does this mean? Thanks for your help!

The Big Four is formally known as the Cleveland, Chicago, Cincinnati & St. Louis. It was a component of the New York Central by way of a long-term lease.

Thank you!

Minor quibble, but the cities were arranged in geographic order from E-W. Clv, Cin, Chgo &StL.