Here is a picture of several issues of the Federal Register. The issues on the bottom of the stack are the typical size of an issue. A typical day usually runs 200-300 pages. Maybe the thin issues are weekend editions? No, the Federal Register is published during the business week. The thin issues are from the days when the government shutdown was taking place.
The October 17th, 2013 issue is 5 pages long and has two entries. One is a Coast Guard, Temporary final rule, and the other is a final rule from NOAA.
These thin issues raised a thought about the nature of print and electronic publishing. In a print world you notice the size of each Federal Register issue. In a digital format a fat issue or thin issue is just a link among other links. One one level this may not be important but other times you can glean that things are happening when you notice a particularly large or small issue of the Federal Register.