Half drop: the offset strip
Why alternate drops need an extra half repeat.
Half drop shifts every second strip by half a repeat. A 64 cm repeat offsets the odd strips by 32 cm. To keep a full motif after that shift, the cut gets longer: wall 240 cm + allowance 10 cm + half repeat 32 cm = 282 cm, rounded up to 5 × 64 = 320 cm.
Same wall and same 10.05 m roll: 320 cm fits 3 times (960 cm) with 45 cm left on a full roll. Eight strips still need 3 rolls, but the leftover on the first two rolls is only 45 cm, not 237 cm. The third roll holds the last two strips and keeps about 365 cm.
Use half drop for that default. The drawing offsets the guide lines on alternate strips. This is a valid layout, not a claim that no shorter layout exists.