Good evening,
First, a small correction: the authors chose 1114 to be a good depth. 114 reads per sample (10x less) would probably too little in most situations.
Before they choose 1114 to be the cutoff, the authors ran the script 'biom summarize-table'. Have you ran this script yet? It shows you how many reads are in each of your samples. After seeing seeing, this you get to choose which samples to keep and which ones you want to throw away. Like the author say, "so this is always a trade-off between the number of sequences you throw away and the number of samples you throw away."
What does your 'biom summarize-table' look like for your data?
Colin Brislawn