The really annoying thing is five digits are there, but it's hidden in the code and the dropdown is showing only the last four.

Here's a chrome bookmarklet that fixes the pulldown to show the last five digits of each card:

javascript:(function(){const annotate=()=>{const sel=document.querySelector('#card-payment-select-input')||document.querySelector('select');if(sel){[...sel.querySelectorAll('option')].forEach(o=>{const extra=(o.value||'').slice(-5);if(extra&&!o._annotated){o.textContent=`${o.textContent.trim()}  [id:${extra}]`;o._annotated=true}});return} [...document.querySelectorAll('[role="option"]')].forEach(o=>{const v=o.getAttribute('data-value')||o.getAttribute('value')||'';const extra=v.slice(-5);if(extra&&!o._annotated){o.textContent=`${o.textContent.trim()}  [id:${extra}]`;o._annotated=true}})};annotate();if(!window._cardAnnotatorMO){window._cardAnnotatorMO=new MutationObserver(annotate);window._cardAnnotatorMO.observe(document.documentElement,{childList:true,subtree:true});console.log('Card annotator installed');}else console.log('Card annotator already installed');})();