Hi Chris,
Thanks for raising this in the community! Changing the size of the barcodes in Breww for your permanent container labels is not currently possible. If this is something you would like us to look into, you would need to raise a feature request for customisable permanent container labels. It is, however, possible to edit the barcode size on stock labels using custom label templates if I have misunderstood and it is those labels you are looking to edit rather than the permanent keg/cask labels.