EIR Aux save stats - help / advice please

[PolishRick]

Im kind of new to using AB but have just done a list for my EIR and noticed the save stats for Aux inf & Cav show two values ie - 6+/4+ ?.
The 4+ varies dependant on options taken, if i do not take light armour the save stats show 6+/5+, however i still not sure why it shows two stats and also i think the stat that varies on options taken is incorrect, should it not be 6+ save with shield and if light armour taken it should then improve to a 5+. i am still unsure what the left hand stst of 6+ is telling me?
I may be missing something as i am rather a novice with WAB and AB but would really be gratefull of some help with this.

Many Thanks, Rick.