On my AA statement "redemption bonus" refers to the 10% bonus you get on redeeming AA miles if you are an AAdvantage cardholder (e.g., if you redeem a 20k miles award you get 2k miles back if you have an AA credit card). My only possible guess is that if you had both the Barclays and Citi AA cards is that you may have have gotten 10% back twice for each individual card and they are now clawing the duplicative award back.

The miles they are taking back seem rather high for this to be the case, but this is all I could come up with. FWIW, for me, I have both cards and they seemed to apply an even split for a recent 2 person, 80k off-peak award to Europe. This is how it looks in my statement:

AVIATOR 2015 AWARD REDEMPTION BONUS 7/4/15 0 1,000 1,000
CITI 2015 AWARD REDEMPTION BONUS 7/4/15 0 1,000 1,000
AVIATOR 2015 AWARD REDEMPTION BONUS 7/4/15 0 1,000 1,000
CITI 2015 AWARD REDEMPTION BONUS 7/4/15 0 1,000 1,000
AVIATOR 2015 AWARD REDEMPTION BONUS 7/4/15 0 1,000 1,000
CITI 2015 AWARD REDEMPTION BONUS 7/4/15 0 1,000 1,000
AVIATOR 2015 AWARD REDEMPTION BONUS 7/4/15 0 1,000 1,000
CITI 2015 AWARD REDEMPTION BONUS 7/4/15 0 1,000 1,000
Total miles posted 0 8,000 8,000

TM20A EUROPE ECON OW TKT 7/4/15 -20,000 0 -20,000
TM20A EUROPE ECON OW TKT 7/4/15 -20,000 0 -20,000
TM20A EUROPE ECON OW TKT 7/4/15 -20,000 0 -20,000
TM20A EUROPE ECON OW TKT 7/4/15 -20,000 0 -20,000
Total miles redeemed -80,000 0 -80,000