Unable to install 2020-001 security update. Disk does not meet requirements

I downloaded the 2020-001 (High Sierra) Security update https://support.apple.com/kb/DL2032?viewlocale=en_US&locale=en_US from apple's support website . I was successfully able to open the dmg file, but, at the "Destination" select page I received a warning:

"Security update 2020-001 cannot be installed on this disk. This volume does not meet the requirements for this update"

Specs:

MacBook Pro 13" Late 2011

macOS High Sierra v. 10.13.5

Processor: 2.4 GHz Intel Core i5

Memory: 16 GB 1333 MHz DDR3

Graphics Intel HD Graphics 3000 512 MB

I have 118 GB available and the update is 3GB.

As I have a late 2011 model I'm not able to update past high sierra, but I expect that if there is a high sierra update, it should be compatible with my OS.