The rules column in the assets table define the custom rules for each item individually.
The default value of the field would be:
{"core.create":[],"core.delete":[],"core.edit":[],"core.edit.state":[],"core.edit.own":[]}
Which means that all permission rules for this item inherit their permissions from the default global configuration settings as specified for each group.
Otherwise, there are permissions overrides by item:
{"core.create":{"6":1,"3":1},"core.delete":{"6":1},"core.edit":{"6":1,"4":1},"core.edit.state":{"6":1,"5":1},"core.edit.own":{"6":1,"3":1}}
Explanation of the what a value of core.create":{"6":1,"3":0}
means:
For this item the Group ID 6 has Create permissions set to "Allowed" (1), while the Group ID 3 has Create permissions set to "Denied" (0). (ThoseThese permissions override the default global permissions, otherwiseand all other permissions for the rest groups are inherited.)
Hope this helps...