Function scale_duration 

pub fn scale_duration(
    dur: &DurationValue,
    num: f64,
    divide: bool,
) -> DurationValue

duration * factor / duration / factor (#920 Temporal8 [7]). Scales each component by factor, then normalises with the openCypher “approximate” rule: a fractional month overflows into days (× the Gregorian average month length, MONTH_SECS / DAY_SECS = 30.436875 days), a fractional day overflows into the sub-day time, each level truncated toward zero. factor is the multiplier (* n) or 1/n is applied by the caller for division — here we take the already-resolved factor as num with divide selecting 1/num component-wise to preserve precision.