A dot after a note shows that the value of the note is to be half
again as great as it would be without the dot, i.e., the value is to
be three-halves that of the original note.

When two dots follow the note the second dot adds half as much as
the first dot has added, i.e., the entire value is seven-fourths that
of the original note.

When three dots follow the note the third dot adds one-half the
value added by the second, i.e., the entire value of the triple-dotted
note is fifteen-eighths that of the original note.  You will unlikely see this however.