Processing and Formatting Effects > Flame FX > Matte Edge >
Blur Settings

Blur button
  Enable to apply a softening Gaussian blur filter to the edge of the matte.
Blur Width field
  Displays the width of the blur applied to the edge of the matte.
Blur Height field
  Displays the height of the blur applied to the edge of the matte.
Proportional button
  Enable to constrain blur amount proportions.