Chartjs-Javascript not showing up total value in middle of Oracle APEX Donut chart

if I correct understood, try to fix it, add to centerCallback,

var value = dataContext.totalValue;
pieElem.innerHTML = 
      '<div id="myDiv" style="position:absolute;text-align:center;font-size:16px;">' +
          'Total ' + value +
      '</div>';

Could you try this

function( options ){ 
// will hold the total value, must be global variable
var total;

Add below statement in this.pieSliceLabel = function(dataContext){}

    percent = Math.round(dataContext.value/dataContext.totalValue*100);
    total = dataContext.totalValue; //assign to global variable

Update the below innerHTML code in this.centerCallback = function(dataContext){}

  //updated element
  pieElem.innerHTML = 
      '<div id="myDiv" style="position:absolute;text-align:center;font-size:16px;">' +
          'Total' + total +
      '</div>';