12:40 AM, Saturday May 16th 2020
You can go ahead and draw through the point you intended, but ultimately either is fine. One could argue that if the line is that far off, then that is the more immediate issue to address (focusing on your use of the ghosting method), but as far as the box construction goes, drawing through the line would tell you more about your actual intent.
As far as improving your use of the ghosting method, make sure you're doing warmups consisting of 2-3 exercises from Lesson 1 at the beginning of each sitting.