Help with number animation

I’d like to follow on relevant questions. I try to do the animation for number with decimal, but it fails, any suggestion? Here’s my code, for integer numbers it works out well, but for the one with decimal, the decimal part didn’t get count.

let startNum6 = 100.0 ;
let endNum6 = 500.0 ;
const duration6 = 900 ;

$w . onReady ( function () {
setInterval (() => {
countUp6 ();
}, duration6 );
});

function countUp6 () {
if ( startNum6 <= endNum6 ) {
$w ( ‘#text387’ ). text = startNum6 . toFixed ( 1 );
startNum6 ++;
}
}

Anyone knows how to get like 132.1, 132.2,…132.9, 133.0? Right now it will show 132.0, 133.0, 134.0…