Curious about structural calculation

[kaspor]

Hello

Just curious, can someone tell me what the paramaters "Centres (CTS)" and "Design At" for this steel floor beam?

I'm trying my hand at some structural engineering and just need a basic explanation.

Link to calc:

https://drive.google.com/file/d/14JfxSbMs2trF7-461Vhmzp5MdFVmOw71/view?usp=sharing

 

[JStephen]

When I click on that link, I get "No preview available. File is in owner's trash".