This means "Not a Number" - the sheet is expecting an integer and getting something else. I'm not at all familiar with the sheet though, so I don't know why it would be doing that. edit - well I had a quick look, and the price checkbox triggers a worker that calculates the total price from adding cost of the repeating field sections (Weapons/Fittings/Defenses) and adds them to an Attribute @{ship_hull_price}. This Attribute doesn't seem to exist on the sheet - presumably it's a hidden Attribute which should be auto-filled when you select your Hull Type, but currently isn't working. If you know what your hull price should be, you can create an Attribute on the Attributes & Abilities tab, name it ship_hull_price and fill in the price yourself. Unchecking and re-checking the price box should now work - all the prices it grabs from the repeating sections seem to work. The key exists in the code: "hulltypes": { battleship: { ship_ac: "16", ship_armor: "20", ship_class: translate("CAPITAL"), ship_crew_max: "1000", ship_crew_min: "200", ship_hardpoints_max: "15", ship_hp: "100", ship_mass_max: "50", ship_power_max: "75", ship_speed: "0", ship_hull_price: "50000000", but isn't being autofilled for some reason. Someone with better javascript-fu can probably pinpoint exactly what's going wrong, and suggest a sheet fix.