The Blur filter makes your image appear out of focus by randomly displacing pixels. You can alter the amount by which the image is blurred (the distance that pixels are displaced) by adjusting the repeat value (between 1 and 100).
The Random Seed setting controls the randomization element of the blur. Selecting a numeric value here will allow haphazard control of the randomization element of the blur.
A subset of the Random Seed, Time, will initialize every blurring using the clock of the hardware platform. This ensures better randomization results than using numeric seeds.
This slider represents how much randomization will take place during the blur. Higher values will lead to more blurring.
The Repeat slider determines how many times the filter will be used on the active layer or selection. A high Repeat value will lead to more blurring.
Be aware that Repeat sets the number of times the filter runs, so selecting very high values may take a considerable amount of time to render.