This DWORD indicates the size (in bytes) of the section. Because the section size is the first four bytes, you can copy sections as an array of bytes. The section size should always be a multiple of four.
For example, an empty section (one with zero properties in it) would have a byte count of eight (the DWORD byte count and the DWORD count of properties). The section itself would contain the eight bytes:
08 00 00 00 00 00 00 00