Wrong reffers in API-call for referrers with segmentation for search

I have made an API call to

?module=API&method=Referers.getRefererType&idSite=1&period=month&segment=referrerType==search&date=2010-10-01,2011-11-01&format=xml&token_auth=xxxxx

I geht these API-Results:


<result date="2011-10">
<row>
<label>Suchmaschinen</label>
<nb_visits>18288</nb_visits>
<nb_actions>232234</nb_actions>
<max_actions>296</max_actions>
<sum_visit_length>6961834</sum_visit_length>
<bounce_count>2273</bounce_count>
<goals>...</goals>
<nb_conversions>528</nb_conversions>
<revenue>0</revenue>
<sum_daily_nb_uniq_visitors>18160</sum_daily_nb_uniq_visitors>
</row>
<row>
<label>Webseiten</label>
<goals>...</goals>
<nb_conversions>1</nb_conversions>
<revenue>0</revenue>
</row>
<row>
<label>Kampagnen</label>
<goals>...</goals>
<nb_conversions>1</nb_conversions>
<revenue>0</revenue>
</row>
</result>
<result date="2011-11">
<row>
<label>Suchmaschinen</label>
<nb_visits>16539</nb_visits>
<nb_actions>207024</nb_actions>
<max_actions>473</max_actions>
<sum_visit_length>6117479</sum_visit_length>
<bounce_count>2204</bounce_count>
<nb_visits_converted>229</nb_visits_converted>
<goals>...</goals>
<nb_conversions>123</nb_conversions>
<revenue>0</revenue>
<sum_daily_nb_uniq_visitors>16449</sum_daily_nb_uniq_visitors>
</row>
<row>
<label>Webseiten</label>
<nb_visits>98</nb_visits>
<nb_actions>511</nb_actions>
<max_actions>56</max_actions>
<sum_visit_length>8817</sum_visit_length>
<bounce_count>34</bounce_count>
<nb_visits_converted>0</nb_visits_converted>
<sum_daily_nb_uniq_visitors>98</sum_daily_nb_uniq_visitors>
</row>
</result>

How come there are websites and campaigns in there? Isn’t that why I add the segmentation-parameter, to have these not in my results?

I found a work-aorund to this:
I simply added to the segmentation parameters the values


&segment=referrerType==search[u];visitorType==new,visitorType==returning[/u]

Which basically means: “Show me all Visitors that came from a search engine AND are new OR returning.”

Interestingly, I receive a different number of total visits for 2011-11 (as example above): 17,295. Wich is a lot closer to the number the actual PIWIK-Installation throws out (17,310).

But maybe I have a confused thinking-scheme with using the API here.