The documentation says the following.
‘@thissectionnum’
Expands to the number of the current section.
Assuming we are in the second section of chapter three, this value
should be 2. However, `texinfo.tex` does something else:
`@thissectionnum` holds a string that combines the chapter and section
number with a full dot inbetween, i.e., ‘3.2’.
IMHO this is a bug. If the variables held numerical values, it would
be easy to synthesize such a string with
```
@thischapternum.@thissectionnum
```
The opposite, namely to extract the numerical value of the section
number from this string, is possible with some TeX trickery, but this
is against the spirit of the Texinfo language.
BTW, the documentation of `@thissection` is also misleading: the given
example doesn't show the chapter number (followed by a full dot).
Werner
