That behaviour is because Word is trying to keep the columns balanced. If you don't like the results you're currently getting, you could:
1. Delete the paragraph break that appears immediately before the Section break. This won't affect the balancing behaviour, but it will change the balance slightly; or
2. Use Ctrl-Shift-Enter to insert a column break immediately before the entry you want to keep at the top of the right-hand column. Note that this will prevent Word auto-balancing to columns for any further items, so you'd need to move them (or the column break) if you later decide you want a different balance.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]