Slitherine

The picture of p. 26 of FoG rule book (hardback edition 2008) shows a battle group partially disordered when passing rough terrain. The disorder affects only the bases ('A') which are actually on the rough ground. Fair and clear enough. But what if that BG with 3 disordered bases would be charged, in THAT position, by an oncoming enemy BG? Should one consider the WHOLE BG disordered or ONLY the 3 bases ('A') on rough? In other words, during the IMPACT and MELEE phases does the disorder status affect only the bases on rough or all the BG?, and if the former applies, should one apply the 1 dice x 3 penalty only to the disordered bases?
Thanks.

The penalty only applies to dissorderd bases. If the dissordered bases don't contribute 3 dice then no dice are lost.