Numbers in brackets such as this, （一） , are footnotes; click on the number to read the footnote. In the footnote section, clicking "Return to Page X" will return you to that page in the main text.
Characters in angled brackets such as this, 〈通〉 , are corrections or emendations made by the editors. The reason for the correction is usually given in a footnote.
Characters in braces such as this, ｛「戍爻午行克吒成行陰陽之氣而已矣。」韓本有此一段。｝ , are notes or possible additions made by the editors. In the original, printed text, they appear in a smaller font.