That is normal. Credit is measured in points, so those are worth far more points than the standard units (1250 points vs the 200-300 points awarded for the 6 hour units).
Folding whatever I'm sent since March 2006 Beta testing since October 2006. www.FAH-Addict.net Administrator since August 2009.
You can lookup the 3rd party stats provider KakaoStats to get an idea of what work units were 'counted' and how much they were credited for just by going in-depth into the individual Donor stats section.
Cheers
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