If you understand the definition of the unit "cd" for luminous intensity, you can imagine how bright it is.
1 mcd = 1/1000 cd
13000 mcd = 13 cd,
Just imagine there are 13 candles. (don't ask me how big and bright of a candle)
Definition of CANDELA (cd):
Luminous intensity of a point source in a particular direction given by lumens/steradian is the Candela (cd). 1 Candle = 1 Candela. LED output is generally provided in milliCandela or mcd where 1 mcd = 1/1000 cd