I don't think the screenshot is that of a speed alert. Alerts would flash at the top bar in red. The 72km/h sign is part of the map which is probably a Garmin compiled one. MFM's maps are compiled using the cGPS Mapper software. Not sure if cGPS Mapper supports that speed sign feature.
That said, the screenshot is from the recent Nuvi models not the older versions like the 200, 300, 600 and 700 series.
Perhaps Bro Antyong would be the best person to ask.
That is not an active alert. It's just a static reminder of the speed limit on the current road travelled. It will go off once the speed limit changes. This is actually a screenshot of my Nuvi 205W. So...any possibilities of this incorporated into MFM ?