differences Entitlements to Provisioning Constraints
Entitlement for a product in a bundle is the amount (in units of measure) of usage of the product which is included in the bundle and will not be charged in the bundle. You can find explanation on how entitlements are calculated at http://support.citrix.com/proddocs/topic/cpbm-22-map/cpbm-admin-accountingentitlements-con.html.
Provisioning Constraints in a bundle defines what all resources can a user provision when he purchase this bundle.
Hope this helps.