HP 48G Linear Regression Best Fit Line

[MNH]

I appreciate all of the help being offered here! I may be a victim of misunderstanding the mathematical lexicon involved with finding a best fit line (BFL). I recently read on a website that a BFL is an orthogonal projection using least squares. Please look at the attached thumbnail in this thread. The BFL (248 going N. to 254) on the W. side of the street is

248 29945.480 921.773
249 30002.951 922.245
251 30058.926 921.687
252 30114.903 923.001
254 30221.977 924.059

The office software I'm using creates 2 points, which define the BFL as being N 00°28'36" E (azimuth 00°28'36" or clockwise 00°28'36" from the N.). The first of these points is near 248, the second is near 254. The orthogonal offsets to the BFL are

Point: 248 Offset: 0.24655 Right
Point: 249 Offset: 0.24033 Right
Point: 251 Offset: 0.78342 Left
Point: 252 Offset: 0.06476 Right
Point: 254 Offset: 0.23177 Right

I believe I need I to create a new matrix (ΣDAT) in my Emu48. I believe I entered erroneous data after examining a recent post in this thread. If my thinking is correct, the resulting slope will indicate the direction of the BFL. I have to digest all of the information presented here. Again, thank you for the help!