If it's wholemeal then I would count 57g as a HexB and syn the rest. I do the same for rolls, which are never the right weight.
The thick sliced wholemeal granary is 5 syns a slice, so if I had 2 I would count 10 syns and then take off 6 which would be my HexB (any wholemeal bread, 57g) and count 4 syns.