Phab can get into a state where a milestone column on a parent project's workboard displays a different number of tasks then the milestone's workboard does. It seems that tasks tagged with the milestone first and subproject second do not show up on the parent project's workboard. If the tags are reversed then the task will show up.
## Repro Steps
From a fresh install, do the following:
1. Create a project ("SUPER PROJ")
2. Create a subproject ("SUB PROJ"). This converts "SUPER PROJ" to a parent project.
3. Create a workboard for the super project
4. Create a milestone under the superproject ("MY L STONE")
5. Create a workboard for the milestone
6. Create a task. Tag it with both the milestone ("MY L STONE") and the subproject ("SUB PROJ") in that order:
7. Navigate to the workboard for "SUPER PROJ". The column for the milestone will contain no tasks.
8. Click through to the milestone's workboard. The task you created should appear there.
9. Remove both tags from the task and save it.
10. Add both tags back to the task, this time with the sub project tag first and the milestone tag second.
11. Return to the parent project's workboard. The milestone column will now contain the task.
Depending on the order you have the tags, the task will either show up on the parent project's workboard (if the milestone is second) or it won't (if the milestone is first).
```phabricator 9e2f263bb49c3fdc433fbec63ca849ff9e1fa2b6 (Tue, Mar 28)
arcanist d1db9a72b552151613a918e3d49fa72433387a68 (Fri, Mar 24)
phutil c581e769f10c6d2b427900897edba74e01a572bd (Sat, Mar 25)```
I wasn't able to find this described in any existing project task, but I suspect it might be described somewhere in T10349.