diff --git a/_docs/gene-product-association-data-gpad-format-20.md b/_docs/gene-product-association-data-gpad-format-20.md
index f4e7af1c..8dd97df9 100644
--- a/_docs/gene-product-association-data-gpad-format-20.md
+++ b/_docs/gene-product-association-data-gpad-format-20.md
@@ -190,4 +190,4 @@ The Annotation Properties column contains a list of "property_name = property_va
 * model-state=production
 * creation-date=2019-07-20T12:04:08
 
-This field is optional, cardinality 0 or greater; for cardinality >1 use a pipe to separate entries.
+This field is not mandatory, cardinality 0, 1, >1 ; for cardinality >1 use a pipe to separate entries