Both build numbers
15.0.4571.1502 refers to your farm has been patched to Service Pack 1. you can check the corresponding release for the build numbers at SP Build Number
Regarding The first number
15.0.4569.1000 is Service Pack 1 (replaced) that released on 2014 February 25.
Regarding The second number
15.0.4571.1502 is Service Pack 1 (re-released) that released on 2014 April 22. Note: re-released means SP1 has been updated for more details check SP1 for SharePoint 2013 has been rereleased
Note: Don't trust the build number in Manage Servers in Farm, it often gives you a wrong indication about installed fixes. For more details check SharePoint patching demystified
KB2880552: it's the knowledge base number of the description article related to this update.
The description article shows How to obtain and install the service pack, the fixes, and the prerequisites ...etc
See also FIND FARM PATCH LEVEL / LATEST CUMULATIVE UPDATE THAT HAS BEEN INSTALLED ON SHAREPOINT FARM