Pattern Help needed

In my pattern it calls for me to knit 13 , CO 1 st , knit 1,etc…
What does “CO 1 st” mean?

it depends on the pattern. It could be cast on one st but it could also be cast off one st and there’s obviously a big difference. Your pattern may give you a list of abbreviations.
Can you give us a link to the pattern or the pattern name?

It’s Pattern #KHCAfghan. I appreciate the help

Thank you for the pattern. On the initial page there’s a table of abbreviations. It defines CO as cast on (BO is used as bind off). You can use a backwards loop cast on for this single stitch if you like. It’s demonstrated on this page (under Free Videos at the top of this page, Increases). It’s a lovely pattern. Enjoy knitting it!

Yeah, I think a backward loop ‘CO’ would work as that’s also used as an increase. A knit CO would be much more obvious.