Hola Ashlyn

It'd be necessary to see the context where you found that sentence, but it looks like a "que" that is simply emphasising what is said next, there is no straight forward meaning for that que, really. This is why we don't have a lesson on that specific use. It is colloquial. 

Que ya voy... could be said by someone that has already been asked to go somewhere; imagine a toddler calling her mum lots of times while she is busy and trying to ignore the toddler; when the mum finally gets a chance to go play with the toddler she finally says "que ya voy..." - that que would be emphatic. 

I hope it clarified it. 

You may be interested in this other use of que, which is similar: 

Que introducing a warning or a threat in Spanish

Saludos