This warning is generated by apache fop which is the library of apache for generating pdf's using xslfo's.
Basically what it sais is you (or mendix) defined a size of your region-before (usualy a header or title of something) area but its contents require more space. This results in overflowing contents and could lead to ugly pdf's.
The second warning is kind of the same warning but then for some paragraph which has a predefined size but it is overflown by 10442 millipoints
Why mendix is suddenly showing these warnings i don't know. Perhaps they updated the fop library or maby they thought that it could help you debug your pdf's better.