When using Count(fld, confld, cond) in crytal report, if confld is a boolean field, how to write cond?

In Crystal report document, they give the following description about how to use Count:

Count(fld, confld, cond);

    *  cond is a String indicating the type of grouping for condFld. You only specify this argument when condFld is a Date, Time, DateTime or Boolean field. For more information on the valid strings for this argument, see Conditions for summary functions.

Boolean conditions
      
    * on any change
    * on change to yes
    * on change to no
    * on every yes
    * on every no
    * on next is yes
    * on next is no

But there is no example. Could someone give me examples about how to write those Boolean Conditions when using count function? Thanks a lot.