Can't bind to 'aria-valuenow' since it isn't a known property of 'div'

Angular2 binding is property binding by default. There is no aria-valuenow property on div if there is no directive or component applied that has such an @Input()

Use instead explicit attribute binding

attr.aria-valuenow="{{MY_PREC}}" 

or

[attr.aria-valuenow]="MY_PREC"