The box normally has them all in numerically
How are you going to detect if the numbers are not sequential?
Even if they are sequential how will you know what the number of the "first" canister in a box is?
Those photographs show a weight, don't you have to include that in the paperwork?
What exactly do you mean by "Count out the number of cans I tell it I need"?
You might be better to tackle the root of the problem and get your supplier to provide canisters with barcodes and delivery notes in electronic format.