Is it the symbol for brake fluid (circle with solid brackets around it and a wobbly line across) in the square display, with a date below in the main rectangular display? If so, then it's a brake fluid change. on cars built before Mar 2011 brake fluid change is due every 2 years. Cars built after Mar 2011, it's 3 years. The first brake fluid change is covered under the TLC pack (I've just booked my car in for it and the dealer confirms this). TLC terms are on the Mini website (this site won't let me include a URL in my post as I'm new) - do a google for mini tlc terms.
If it's not the above and you're seeing a circle with brackets around it and an ! in the middle, that does indicate low brake fluid. The handbook says to contact your dealer for service for that, which makes sense as low brake fluid indicates a leak somewhere.
However you deal with it, do deal with it though - brakes are pretty important
All the best,