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). (These permissions override the default global permissions, and all other permissions for the rest groups are inherited.)
 
Hope this helps...