This situation occurs when a LR image has been modified in LR and it has also been edited in another external app, giving two possible sets of "true" metadata. In this case, you will have to decide whether the external settings are correct, or are the ones from LR correct. If you think that the ones from the external file editing are correct, then you can choose to "Import Settings from Disk". If you decide that the Lightroom catalog settings are the more correct version, then you can choose to "Overwrite Settings". Whether or not it has anything to do with DPP, will depend on what you were doing before you got the message. My guess is that you have probably gone into one of the plugins, made some changes and then returned to LR and made some more changes. I think, also, that a lot of this depends whether or not you have the "Automatically write changes into XMP" turned on. If not, then you can use the Metadata>>Save Metadata to Files command in the Library module, or the Photo>>Save Metadata to Files command in the Develop module. HTH.
Cheers,
WesternGuy