Further to my comments on the ByT, it should be realised that there are number of copies of this document, none of them original. In the 1950s Thomas Jones looked at the various versions together with the Cronicon de Wallia. Together with the Latin texts known as the Annales Cambriae they can be found on http://croniclau.bangor.ac.uk/ the Bangor University site of the Welsh Chronicles Research Group.
There they suggest that the Peniarth version written/collected in the 14th century is the best.
So although the Gwentian Chronicle was based on all/some/part of these versions, I must retract my comment that ByT should NOT be used, and say it should be used with caution.