is conditionally required, repeated in added text and extra s.   

existing:

2A.2.28.3 Field Position (SI)
Definition: Identifies the number of the field within the segment. The first field is assigned a number of 1. Field number should not be specified when referring to the entire segment. This field is conditionally required, is conditionally required when Field Repetition (ERL-4) and/or Component Number (ERL-5) or ERL-4 Field Repitition are s populatedwhen Component Number (ERL-5) is populated..

suggested:

2A.2.28.3 Field Position (SI)
Definition: Identifies the number of the field within the segment. The first field is assigned a number of 1. Field number should not be specified when referring to the entire segment. This field is conditionally required when Field Repetition (ERL-4) and/or Component Number (ERL-5) are populated.