Length of garment + Length of Sleeves (if any) = fabric consumption estimate*
50 cm = garment length
54 cm = sleeve length
104 cm = fabric consumption estimate
* based on the assumption that front and back of a garment fit into the width of the fabric being used. In some cases (very loose wide robes or Kaftans) it can bee that this does not work (because the garment is so wide).
In such a case you'd take garment length x 2 + sleeve length = consumption estimate.