These are numbers including integers and all the other numbers with values present between them such as 22/7, 2.5, square root of 5 etc.
Cracking the GRE, 2010 Edition (Graduate School Test Preparation)
Kaplan GRE Exam Vocabulary in a Box
Essential Words for the GRE (Barron's Essential Words for the GRE)
Kaplan GRE Exam 2010-2011 Premier with CD-ROM (Kaplan GRE Premier Program (W/CD))