Extendscript create bars and tone timebase

Hi folks

I'm trying to create bars and tone programmatically using the API. I can't figure out the format of timebase, it either fails or creates a 29.97 bars and tone (I want 24fps)

Docs say

app.project.newBarsAndTone(width, height, timeBase, PARNum, PARDen, audioSampleRate, name)

Here's what I've tried.

Fails     

var audioSampleRate = sequence.getSettings().audioSampleRate;



var bars = app.project.newBarsAndTone(1920, 1080, "24.00", 1, 1, audioSampleRate, "filler");

var bars = app.project.newBarsAndTone(1920, 1080, "24.00 fps", 1, 1, audioSampleRate, "filler");

So it's not a string, even though the docs say a timebase is a string

Sequence.timebase¶

app.project.sequences[index].timebase

Description¶

The number of ticks per frame in the sequence. Converted to seconds, this is commonly referred to as the frame duration of the sequence.

Type¶

String; read-only.

Creates 29.97 , which is assumed is the default?   

var bars = app.project.newBarsAndTone(1920, 1080, 24.00, 1, 1, audioSampleRate, "filler");

var bars = app.project.newBarsAndTone(1920, 1080, 24, 1, 1, audioSampleRate, "filler");

var bars = app.project.newBarsAndTone(1920, 1080, 10584000000, 1, 1, audioSampleRate, "filler");

var bars = app.project.newBarsAndTone(1920, 1080, sequence.timebase, 1, 1, audioSampleRate, "filler");

Can anyone help with the correct parameters?