preview: number of columns and rows

[peter]

hello,

i switched the number of columns and rows from 7 x 9 to 7 x1o and found for smaller clips only the same picture 70x in the preview (with 7x9 there are different pics).

in bigger clips even settings with 9 x 25 are working fine.

is there a certain relation needed 'duration/number of pics' to avoid 'one pic-previews'?

thank you