That "green arrow" indicates that that particular Constraint has been 'overridden' relative to some other part of the Assembly. What this does is allow you, for a specific situation where this assembly is being used, to override the original Assembly Constraints assigned to that assembly.
For more information about how and why you would do something like this, I would go to the 'Help Files' and search on "position override".
John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
