getTimeSteps - what's the 3rd number in the output

Help shows
[font=courier]getTimeSteps(...)
    Fetch list of time steps stored in the current DAC file.
    SYNTAX: <list_of_steps> getTimeSteps()
    RETURNS: a two-dimensional array of time steps
            index 0 contains the simulation step number (may be different from index on sparse DACs)
            index 1 contains the simulation step time[/font]

However my output looks like this:
[font=courier][(0, 0.0, [b]0.0[/b]), (88, 3653.0, [b]3653.0[/b]), (139, 36554.0, [b]32901.0[/b]), ...] [/font]

What's the 3rd number in there?

Thanks, Chris