Can you help? 'valid thru' question - card validity

[aislealways]

What does 'valid thru' mean on a elite gold members card? I just checked in with the card and then was told I was now silver, which I knew, but no lounge. Although I did get lounge on the outbound?

So what does the 'valid thu' actually meant? Was I just lucky SIN-LGK to get lounge access?

Yours, clueless in Starbucks Langkawi :-)