A data frame has been specified whose Y-dimension is different from that of the first frame specified during the reduction. All frames must have the same X- and Y-dimensions. The most likely cause is that the frames are from different datasets. If you really want to use this combination of data frames then you must use the facilities of FIGARO to `grow' one of the data frames up to the dimensions of the other. Take care to ensure that any image registration problems are removed before reduction is attempted. In general it will be necessary to re-start the reduction with a new reduction file after any such adjustments have been made.