Having worked in a local authority, these questionnaires from third parties are hardly ever filled in by someone at a senior level, if they are filled in at all. At best, some poor clerical grade worker will have been given it and a printout or access to the relevant finance codes and told to sort it out and if they're lucky, someone senior might actually read the results before signing and sending it out. Unless it's statutory, these things are at the bottom of the priority heap for most local government managers.
On the junior employee's screen will not be the invoice details but something like "Item quantity: 1, Item description: SD card(s), cost: X pounds" and 1 and X gets put in the boxes. Could have been 1 card or 1 pack of 20 cards or a 100 of them for all we know. Seen too much of this to be surprised and the recipients rarely query obvious errors - they just publish it anyway.