There is two parameters in jcr QueryHandler configuration:
Minimal distance between checked word and proposed suggestion;
Search for more popular suggestions;
<query-handler class="org.exoplatform.services.jcr.impl.core.query.lucene.SearchIndex">
<properties>
...
<property name="spellchecker-class" value="org.exoplatform.services.jcr.impl.core.query.lucene.spell.LuceneSpellChecker$FiveSecondsRefreshInterval" />
<property name="spellchecker-more-popular" value="false" />
<property name="spellchecker-min-distance" value="0.55" />
...
</properties>
</query-handler>
Minimal distance is counted as Levenshtein distance between checked word and spellchecker suggestion.
MorePopular paramter affects in next way: If "morePopular" disabled:
If the proposed word exists in the directory - no suggestion given;
If the proposed word doesn't exist in the directory - propose the closed word;
If "morePopular" enabled:
No matter word exists or not, checker will propose the closed word that is more popular than the checked word.