filter with comparaison >= or < operator

["eric German" <eric.german@waika9.com>]

hi, i m trainning a filter like this :
"cn>= germ" with openldap 2.0.7 on linux 

first : i must change schema (ordering) the name .
second : results are not alway  matching the condition . why ? 
 
is the condition in filter work fine ? 

thank 
eric german