>just have an @ at front
This just means they contain vertical version of the font (a sort of hack, typically for certain Chinese, Japanese and Korean fonts, the idea being that if you want to generate vertical text, you start with the horizontal version of the font and compose your document, then switch to the vertical version for printing)
>a document with 340 fonts ... found 502 items
There are a whole bunch of reasons why some fonts are sometimes hidden from applications (no point listing them if the application can't use them, for example)
>"*.ttf" and found 1,353!
A single font (family), containing various styles, may consist of multiple ttf files. Arial would be good examples, consisting of 9 ttf files