I have 600 series and I want to calculate the MASE for horizons 1, 3, 6, 8, 10 and 12. I've seen the work of Nikolaos Kourentzes where he calculates an ASE (no Mean) for each of three time horizons for thousands of series and then averages the ASE values across all series for each horizon to get a single MASE value. I thought the MASE was calculated only for each series, but now I'm confused.
Can I also calculate the ASE for each series at each horizon and then average across all series?