Level at which GTIN is to be validated.
Any level (level is ignored).
Retail consumer trade item level, supporting GTIN-13, GTIN-12 (optionally zero-suppressed), and GTIN-8.
Other than retail consumer trade item level, supporting GTIN-13, GTIN-12 (not zero-suppressed), and GTIN-14.
Level at which GTIN is to be validated.