For example if we have goods in cartons . its weight is not same always one may contain 10kg another may 20kgs or another may have 5kg etc .
i.e product A is in 10 carton total 200kg.

example 1. if customer ask 10 kg we give 1 carton to customer and invoice for 10kg.

example 2. if customer ask for 18kg . we move close to matching carton . say 3 cartons comes to 19kg . then we should ship 3 carton and invoice weight is 19kg

how to handle these kind of variable weight and carton unit in odoo