Javascript Timing: Control page time with decimal numbers

I want to control page viewing time. I used "seconds to count" of timer option in the question editing pane before.
However, "seconds to count"  can only set up integer numbers. But I want to fix the page viewing time in a more precise manner, with decimal numbers.
Could I change scripts in the qsf file directly and upload it into qualtircs?
For example, below in a normal qsf script about timer
{"QuestionDescriptionOption":"UseText","MinSeconds":90,"MaxSeconds":39,"ShowTimer":true,"Seconds":39},
And I modify "MaxSeconds":39 to"MaxSeconds":39.5
Will it work?
Or I must use Javascript to modify the page viewing time. Like what this page said, change the Javascript for the first question in the page.
Now, I did not have the premium account in qualtrics. So i cannot try directly.
Thank you for your help!