How long will it take for me to get an "A" school ship date?

I am prior service. Just swore in with the USNR today: LSSN. The A school (in Mississippi) is not required but I am opting to go. They said the need 5 days to get me into the computer system, then I can talk to someone about going. I am wondering if I will be able to ship out right away, or if I am going to be waiting a while. I am looking for advice from someone with experience! Thank you.