FASTICA algoritm produce independent components does not equal to the dimensionality of EEG signals
ICA can be seen as a dimension reduction technique similar to PCA.  Although PCA consists of the eigenvectors of the covariance matrix i.e. second order statistics, ICA is not restricted and can contain higher order stat. The goal of ICA is to span the signal space in the most statistical independent vectors. So you might get a considerable dimension reduction.