Shell Count unable to set to 0?

Currently own a guider 2 and planning to print as follows:

• TPU
• 0.2mm layer height
• 0.4mm nozzle
• No support structure
• No walls, top or bottom layers, just print the inside
• 20% filling “Gyroid”

For my print preview and in print settings im unable to set shell count as 0. Anyone able to assist?

FYI i want to print the Inlet V3 shown here