if I navigate to the Campaign Group stats edge https://developers.facebook.com/tools/explorer/539923059395125/?method=GET&path=6008937476954%2Fstats%2F1409544000%2F1409630400%3Ffields%3Dspent%2Cid%2Ccampaign_group_id%2Cclicks&version=v2.1 (or 6008937476954/stats/1409544000/1409630400?fields=spent,id,campaign_group_id,clicks in the graph explorer), I get:
"spent": 2722670,
"campaign_group_id": "6008937476954",
"clicks": 100557
This is a spend of $27,226.70.
If I navigate to the matching Account stats edge (act_1376129679277116/stats/1409544000/1409630400) in the Graph Explorer, it returns $1,099.61 which is correct (as is the Ad Sets stats edge). So it seems that just the Campaign group edge is (very) incorrect.
Anyone else seeing this?