Potential Typo in QuickStart

[Chen-Suyi]

Thank you for your significant contribution to this field. I am extremely interested in your work, and I am now following it. However, I face some problems while reproducing the results.

Referring to ValueError: setting an array element with a sequence. #428

double options '-D' exist in the following command for downsampling the image stack.

cryodrgn downsample shiny_2sets.star --datadir 10028/data -D 128 -o particles.128.mrcs -D 50000

It seems that -D 50000 is a typo. Could you please revise it and provide the correct command for this step?