These are custom objects in your schema, so we cannot tell you, it depends on how the tables have been created.
If I had to guess, you probably have a
contact <-- invoice <-- invoice line model,
By which a lead/contact or account can have 1 to many invoices attached and each invoices will have from 1 to many invoice lines attached.
Your model can be checked in the admin->salesforce object sync or admin->Marketo custom objects
If this is correct, "Has invoice" means there is an invoice header attached to the lead/contact or to the account, while "Has invoice line" means not only the lead/contact or account has an invoice but also this invoice has lines.