There shouldn’t be an issue using a large number if you display it big enough (a QR code can store up to thousands of characters), however, when it comes to scanning, the smaller the better.
There are also many reasons why there could be some issues with the QR code scanning (brightness of the screen, scanning distance, your camera’s focus, the cleanliness of your lens, the size of the displayed QR code, QR code not displayed entirely…).
If you think it is not related to any of these cases, could you provide me as much of the following informations as you can to help me find the issue :
- Your apps’ version
- Your phone’s model
- Your android version
- In which case you use the QR code scanning (search a record in the listing page, fill a field’s value, to select a field when you filter…)
- QR code number(s) with which you encounter an issue
- Do you have some crash or error message when you use the QR code scanning ?