Symbol LS 5700 Product Reference Manual page 237

Parameter Menus
Decode Options
UPC/EAN Security Level
Level 1
As bar code quality levels diminish, certain characters
become prone to mis-decodes before others (i.e., 1, 2, 7, 8). If
you are experiencing mis-decodes of poorly printed bar
codes, and the mis-decodes are limited to these characters,
select this security level.
UPC/EAN SECURITY LEVEL 1
5-173