600 lbs so a little over 23lbs per bird. This is only our second batch of Cornish cross so I'm not sure if I can cut that down. Yup, processed 2 days shy of 9 weeks
Discussion
We typically feed out about 18 pounds per bird when processing at 8.5 weeks. We weigh out feed every day starting around day 3-5. We grabbed a Cornish feed chart online based on age but cut that about 10% for pastured chickens (reduced mortality from otherwise growing too fast). Our weights are similar to what you referenced. Typically the second batch of the year processed in July is our best feed to weight gain ratio due to most favorable weather. Ensuring they have soil and or grit helps improve feed efficiency as well.
This is the chart I used, but I didn't cut any to account for them being pastured. I'll try that next time. 
Don't cut on account of being pastured. Only if you experience mortality that you think is related to growing too fast. Signs of that would mostly be pale combs/wattles, no longer able to stand/walk, etc.