Here 3/5 means three "fifth notes" per measure just as 3/4 means three "fourth notes" per measure.
To get the pitches, you choose a pitch for the 1/1 and then all the other pitches are related to each other in the same ratios as the rhythms.
The way to understand this is: a 7/4 would have 7 beats for every 2 beats of the 2/4. So the 7/5 goes 5/4 times faster, so 35 beats for every 8 beats of the 2/4
Similarly the 7/5 has 35 beats for every 12 beats of the 3/4 - and it has 7 beats for every 3 beats of the 3/5, so at 35 beats of the 7/5, they all come together - which happens just after 29 seconds into the movie.
There I'm using the convention that in a polyrhythm such as 7 : 3 or 3 : 2 with the measure sizes the same then you use quarter notes to notate all the polyrhythms. So then you have to interpret 7/5 and 3/5 etc as in the video.
You could alternatively use four "quarter notes" to a measure and so notate e.g. 5 : 3 using fifth notes and third notes, and if you did that then the 7/5 is beating 35 beats every 4 measures, so you would notate it using 4/35th notes and the time signature then would be 7 / (4/35) but that gets rather awkward