The feature level indicates the functionality of the product and is usually applicable to font encoders and tools.
The feature levels are as follows:

Feature Level:

Description of enhanced functionality:
1 Supports the basic functionality of Code 39 or Codabar barcodes without check digits or a single advanced symbology such as Code 128.
2 Supports most linear barcode types including Code 39, Code 128 sets A, B and C, Postnet, MSI, Interleaved 2 of 5, UPC-A, EAN-13 and EAN-8.
3 Supports the previous level and adds UPC-E, Code 128 Auto and 2 or 5 digit add-ons for UPC and EAN.
4 Supports the previous level and adds functionality for FNC1 codes in GS1-128 only as character ASCII 202 in Code 128 Auto as described in the Code 128 FAQ. Does not support ApplyTilde commands.
5 Supports the previous level and adds functionality for Code 128 auto as described in the Code 128 FAQ for FNC2 and MOD10 calculations with the ability to format the AI in the text interpretation of the barcode from 2 to 7 digits. Supports all Code-128 ApplyTilde commands.
6 Supports the previous level and adds functionality for 6, 7 or 8 digit numbers as the input for UPC-E, UPC-E system 1 compatibility, UPC-E automatic switching between system 0 or 1, improved Code 128 number compaction, SpliceText option for improved readability of long numbers in the text, support for a large amount of data in code 93 and White Space Increase in applicable components which improves readability when barcodes are printed on ink jet printers.
  7 Supports the previous level and adds functionality for the USPS Intelligent Mail Barcode, also known as OneCode Solution 4-State Customer Barcode.
D Refer to the documentation for this products features.
M If this product is a barcode font it supports multiple feature levels depending on the font tool used. Therefore, please refer to the font tools section for the features supported.