I'm confused!!!

There are Preferences on each host.
And more Preferences in each account on the Projects' websites.
The Resources column in Boinc Manager doesn't behave as I expect when I modify the above Preferences.
Somehow boinc decides what Tasks to download to the client.
The client decides what Tasks to run.
There are cryptic messages in the Event Log.
There are hosts with different resources and different sets of projects.

Is it any wonder I'm confused?

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There are Preferences on each host.

The one is use most is the percentage of cpus to use. Also I always ensure leave running tasks in memory while suspended is ticked as in my main project it reduces crashes.

And more Preferences in each account on the Projects' websites.

The main one I use of these is the resource share which sets how high a priority a particular project has. Some projects allow you to set what type of tasks they will send you. They also allow you on some projects to set the maximum number of tasks of a particular type to run at once. (WCG by default only allows you to run one Africa Rain Project task at once.)

The Resources column in Boinc Manager doesn't behave as I expect when I modify the above Preferences.

How do you modify it and what do you expect? Predicting how it will behave is particularly difficult if you have projects with widely differing deadlines. E.G. some having only a day or less and another over a year as in CPDN. The mechanism wasn't really designed to cope with extremes like that.