What does it mean if a process has an O or an I at the start of the line?

After running ps, I noticed that a couple of the processes had an O at the start of the line. In all my years, I've never seen this. I thought that the meaning of the indicator might be common knowledge, but I asked my circle of software professionals and they had no idea either. The column isn't labelled, either. I read the entire manual entry for ps and couldn't find what it means; there's nothing about an O. It might just be unique to MinGW. It appears even when ps is the first command entered in a fresh console. Any ideas? And in text-based form:

$ ps
      PID    PPID    PGID     WINPID   TTY         UID    STIME COMMAND
     9484    5176   17152       1172  cons0       4096 14:35:31 /usr/bin/sh
I   21164   17156   21164       4320  cons2       4096 16:11:48 /usr/bin/ssh-keygen
    19220       1   19220      19220  cons0       4096 14:34:10 /usr/bin/bash
    16344       1   16344       7392  cons3       4096 10:53:33 /usr/bin/bash
    17156       1   17156      17156  cons2       4096 16:09:52 /usr/bin/bash
    23660   23740   23660      18060  cons8       4096 08:28:14 /usr/bin/ps
    17152   19220   17152      17152  cons0       4096 14:34:10 /usr/bin/bash
     2552       1    2552       2552  cons6       4096 14:14:52 /usr/bin/bash
     4904    9484   17152       4704  cons0       4096 14:35:31 /c/Program Files/nodejs/node
     7396       1    7396       7396  cons7       4096 08:23:44 /usr/bin/bash
    23740       1   23740      23740  cons8       4096 08:28:11 /usr/bin/bash
    17020       1   17020      17020  cons1       4096 15:16:26 /usr/bin/bash
     5176   17152   17152      12140  cons0       4096 14:34:15 /usr/bin/bash
I   15460       1   15460      15460  cons4       4096 16:18:14 /usr/bin/less
    20616       1   20616      20616  cons5       4096 16:21:36 /usr/bin/bash