Jaffa3D

Hi, I'm a mega noob and have not printed anything yet on my E3D Bigbox yet that I have got working after someone gave up on after fitting with a Duet wifi board and 7" paneldue. I fitted a BLTouch and the machine seems do do everything I've asked ie dual Z motor levelling, mesh compensation etc but I'm about to start my first print using Cura 4.7.0 to slice the stl file and I've noticed a couple of things that I would like to clarify before starting. I'm editing the start G-code to incorporate the levelling etc and I notice an M24 command without a preceding M23 command choosing a file. I presume this will just start the print anyway but would like to know anyway. I think I understand all the start sequence but at the end there are a few lines I don't understand their purpose. They are highlighted red :- 159.688 Y74.363 E2343.13956 G1 X159.547 Y74.363 E2343.14007 G1 X159.397 Y74.513 E2343.14085 G1 X159.397 Y74.372 E2343.14137 ;TIME_ELAPSED:2942.734487 G1 F1500 E2341.14137 M140 S0 M204 P3000 M204 T3000 M566 X1200 Y1200 M107 M83 ;relative extrusion mode M104 S0 ;End of Gcode What would the G1 command do as I would think it would extrude 2.3 meters of filament at 1500 mm/min after the print finished ??? I'm also puzzled as to why the M204 and M566 commands would modify movement parameters after the print had finished and no more movements expected. I suppose I could just try it as is but I would like to get it as right as possible before starting. Thanks in advance for any help.