sless2,
Those lines on the firewall would be there to give you a reference point for the center of your motor mount. If you have a one-piece motor mount you'd simply align it to those lines so that the intersection of those lines is exactly in the center of the mount. chuckle... Of course, those lines don't exist where that intersection would be, and the exact center of the motor mount is just air too.... But you get the idea.

I'm assembling a Cap232 right now too. Mine however is a KYOSHO .46 size, but it's also got the hole and reference lines. The idea is that you're going to have to position the motor mount to the side and up-or-down in order to have the prop tighten down on the engine thrust washer in the center of the spinner opening in the fiberglass cowling. If the airplane has right thrust (which yours looks to have) then the mount will be positioned somewhat to the "left". And the same idea if the plane has up or down thrust.

One good way to assure that you're about to drill the holes in the right place is to attach your engine to the motor mount and tack glue the mount where you think it should go. Then slide the cowl on and see if the thrust washer is centered in the cowl opening. I'm just about to do that myself. It's important to do this check because ARF makers are often just toy manufacturers. I've had 2 ARFs recently that said they had no thrust offset in the model, yet did. And not only did they have thrust offset after saying they didn't have it, but one of them actually had the reference lines and access hole drilled for UP THRUST when the bloody model had DOWN THRUST. That one would have looked really stupid had I placed the motor where the reference lines showed. The prop would have been "centered" way off center in the cowling.

Don't trust anything the mfg's manual says about an ARF. Those people aren't blessed with perfect translation skills and aren't always very talented at manufacturing flying models either.