Two stereocenters: one configuration, four drawings

Both are drawn from the 3D model. Left: the line-angle drawing, anti chain in the plane of the page, solid wedge toward you, hashed away. Right: the Fischer projection, chain vertical with C1 at the top, eclipsed, vertical bonds away from you, horizontal bonds toward you. Think of the line-angle chain as a mountain range seen from the side: the Fischer projection looks at it from the valley underneath, so every carbon of the chain points away from you and every substituent hangs toward you. Press Fischer to see the model from exactly there. Each drawing’s own R/S is re-derived and compared with the model’s.

Turn the C2–C3 bond through every angle: the (R)/(S) labels never change. Fischer uses the eclipsed (0°) form, zigzag and sawhorse the anti (180°) form; Newman works at any angle.