It will take the access rights with OR condition of those 2 access lines

access1, base.model_res_partner,1,0,0,0
access2, base.model_res_partner,1,1,1,0

Output will be a OR condition of both access (1,1,1,0)

Note:
So, you should always overwrite existing access to satisfy your condition.
i.e. change the access available in odoo modules by using id="MODULENAME.EXISTING_ID"

E.g. to change access
base.access_res_partner_group_partner_manager,res_partner group_partner_manager,base.model_res_partner,base.group_partner_manager,1,1,1,0