Current Week Minicalendar Offsets are used to shift the contents of a minicalendar a given number of weeks with respect to the current week (as determined by the DayValue of the minicalendar token).
Using the token and modifier [mc+00:-2w] produces a minicalendar which always starts 2 weeks before the current week displaying the current week in a central position (IMPORTANT: in minicalendars you can only use week offsets, such as :-2w or :+3w, as offsets specified for a number of days or months, such as :+5d or :-1m, are Date Offset Suffixes which behave very differently).
Note that, to obtain the above result, you need to set the option Show Outside Days of the MiniCal (current) property to true so that the dates before the month are displayed, and you must make sure that fully outside week numbers are not hidden, as is the default behaviour. The correct settings to use are :
However, you do not need to put any tokens in the shaded textbox, since, by definition, it will always remain in the same position.