Storyline360 has GSAP built in. So you should use gsap.set() instead of Tweenlite.set()
@Jurgen Actually GSAP is thus intelligent it uses transforms and will recalculate values.
The error JC made is probably using Tweenlite and thus using outdated code.
https://gsap.com/resources/get-started
By default GSAP will use px and degrees for transforms but you can use other units like, vw, radians or even do your own JS calculations or relative values!
x: 200, // use default of px
x: "+=200" // relative values
x: '40vw', // or pass in a string with a different unit for GSAP to parse
x: () => window.innerWidth / 2, // you can even use functional values to do a calculation!