The task runner defines how DataCleaner's engine will execute the tasks of an analysis job. Typically you shouldn't edit this element. However, here are the two options:
<multithreaded-taskrunner max-threads="30" />
Defines a multi threaded task runner with a thread pool of 30 available threads. Beware that although 30 might seem like a high number that too small a pool of threads might cause issues because some tasks schedule additional tasks and thus there's a risk of dead lock when thread count is very low.
Defines a single threaded task runner. On legacy hardware or operating systems this setting will be better, but it will not take advantage of the multi threading capabilities of modern architecture.