You can "sneak" a day or two or three with layer feed, but you have a loooong way to go before eggs appear. For their optimal health, layer feed is to be avoided. Wait until the egg actually show up. Sometimes that is at 17 weeks, but with many breeds, it doesn't happen until 25 weeks. There is absolutely no rush and no benefit achieved with the layer formula.
I'm a complete neewbie, but as I understand, the layer feed has too much calcium and not enough protein. The protein can always be supplemented but too much calcium will build up and cause problems ( an adult hen would be using it up in shell production ).......I bought a bag a bit early myself...worse yet , Ive gone organic so it was a complete waste. Live and learn...and read BYC!