Hi Moon,
When you installed S/4HANA On Premise 1511, the product was just released barely a week or two.
By that time, the installation was an Initial Shipment Stack, that means most of the software components had no Support Packages by that time.
On february 2016, the FPS01 for S/4HANA On Premise 1511 was released (the also so-called S/4HANA On Premise 1602), delivering the first Support Packages to every software component, thus patching software component SAP_ABA 75A with Support Package 0001.
By May/June 2016, FPS02 for S/4HANA On Premise 1511 has been released.
Best regards,
Esteban