The specification for the human readable interpretation (HRI) expects these AIs to be enclosed in brackets, i.e. (01)12345678901234 for a GTIN of 12345678901234. While this case is easy to handle, there are AIs with a variable data length where a stop character (FNC1) is used to separate them from the next AI. Others have a variable identifier length where one of the digits defines the measurement unit. Without going too deep into the details – this is complex stuff.
A new designer function handles the burden of correctly formatting the HRI for you – you just pass the contents of the barcode and get the HRI with brackets where appropriate.