The “TTG” at the beginning and end of a video clip fill the role that “quotation marks” fill in a news article
In a typical news article, verbatim quotations of what someone said are denoted by quotation marks at the beginning and ending of each quote.
Similarly, TTG-qualified sections within a longer video are denoted by TTG> at the beginning of each of those sections and a <TTG at the end of each of those sections.