General ITF (Interleaved 2 of 5) was designed on top of code 25. It was widely accepted as a numeric bar code symbology in warehouse and heavy industrial applications. The general ITF is continuous and has variable length. ITF has the same encoding technique as for Code 25 with exception that both bars spaces carry information: one character is encoded by bars and the character is encoded by bars and the character next to it formed by the intervening spaces of the bars.
TF-14 is a fixed length. The primary symbol is encoded from fourteen digits consisting of 13 input characters and one calculated check digit. Sometimes there is a add-one symbol next to the primary one with five input characters and one check digit. When you select ITF-14 barcode symbology you will have to enter 13 digits and or 5 additional digits to yield a complete barcode.
Example
