code: function () {
  					var value = this.value,
  						ret;
  
  					if (dateTimeLabelFormat) { // datetime axis
  						ret = dateFormat(dateTimeLabelFormat, value);
  
  					} else if (tickInterval % 1000000 === 0) { // use M abbreviation
  						ret = (value / 1000000) + 'M';
  
  					} else if (tickInterval % 1000 === 0) { // use k abbreviation
  						ret = (value / 1000) + 'k';
  
  					} else if (!categories && value >= 1000) { // add thousands separators
  						ret = numberFormat(value, 0);
  
  					} else { // strings (categories) and small numbers
  						ret = value;
  					}
  					return ret;
  				}
docs: can be overwritten by dynamic format