FCPXML Timeramp (speed) easing

I can't figure how to make easing when speeding in/out

<asset-clip ref="video1" offset="90090/30000" name="11 x.mp4" duration="145145/30000">
    <timeMap>
        <timept time="0" value="0" interp="smooth2" />
        <timept time="2.1624229024943" value="2.1424229024943" interp="smooth2" inTime="0.5" outTime="0.5" />
        <timept time="2.6624229024943" value="20.526577097506" interp="smooth2" inTime="0.5" outTime="0.5" />
        <timept time="4.8248458049887" value="22.669" interp="smooth2" />
    </timeMap>

Currently easing doesn't work...

What inTime="0.5" outTime="0.5" does and what values i should set?