IPv6 Bandwidth effects (EIGRP)

I have noted that different versions or setings of routers have a certain bandwidth level cut off where when reached routes will be changed.That's routes will be selected or changed when they drop below these levels. So far I have noted 3 different cutoff levels 64kbps available bandwidth of 37kbps ; 1180kbp available bandwidth of 885kbps and recently 125ks available bandwidth of 93kbps. This raises a question , is it because of the version of IOS or is it anything to do with router settings? This may need further investigations.