How can I determine steam maximum download speed?

My ISP provider released a data plan of 1GB, which roughly translates as a download speed of 100mb/s.

As an early adpoter of this ISP, I had too many good experiences with them to trust that they would deliver this download speed. However, to my dismay, I cannot surpass the 60mb/s download speed for steam, other than some random spikes.

After contacting my ISP, they claimed that steam may limit trafic on specific times and that is why I cannot get to my dream download speed.

My router is a Gigabit one, so it can handle the internet speeds.

My speed tests show 1 GB on fast and speedtest.

With all that in mind, is there any way to test or guarantee the max steam download speed?

I decided to post here instead of superuser because this may be a question of other gamers