What the numbers are doing
Cost is three lines plus a markup. Filament is grams divided by 1000, times your price per kilogram. Electricity is watts divided by 1000, times hours, times your price per kilowatt-hour. Wear is a rate per hour, the sort of number you get by dividing what the printer cost by the hours you hope to get from it. Markup is a percent of that sum, applied once.
Length and weight use the area of a circle the size of the filament and a nominal density. PLA at 1.24 g/cm³ and 1.75 mm lands near 335 metres per kilogram. A damp spool or a filled filament will not match the table, which is why the material list is editable in spirit: pick the closest density, or treat the result as a starting point.
Print time assumes the model volume is the solid shape, not the plastic a slicer will extrude. Top and bottom layers are solid. Walls are loops around the width and depth you enter. The remainder is multiplied by the infill percent. If you leave the size blank, the estimator uses a cube of the same volume. Send an STL into it when you have a real bounding box.