Uk citizen 144 days transit visa eligibility

Hi I am a UK citizen travelling to Seoul from london. After a few days in Seoul to Busan and then from Busan to Beijing and from Beijjing back to Seoul for a week and then finally back to the UK from Seoul. Am I eligible for the 144 hours twov at Beijing? Slightly confused as it says country A and C needs to be different but in my case both country A and C ais South Korea but not the UK. Any help would be great. thanks a lot :)