Updating my clients routers and the 2860's all come up with a notification when trying to update to 3.8.7

Model Name: v2860
firmware version: 3.8.7_BT
Modem version: VDSL2/ADSL
Current version: 576D17/572801 - 574307/571801
Upgrade version: 576d17/572801 - 574307/571801

The only difference I can see is the capital D is replaced by a lowercase d.
I don't know if its important or if I can just ignore it.