How to format text in the title attribute of <t:outputText>?

I am including a Double in the title of <t:outputText>.  The problem the
  default formating is undesired.
The tag:
  <t:outputText
     value="#{tripSummary.columnValue.idleSeconds.sum}"
     title="Mean idle time is
#{tripSummary.columnValue.idleSeconds.mean} minutes">
   <f:convertNumber maxFractionDigits="0" />
  </t:outputText>

Displays "Mean idle time is 6.977777777777777 minutes"  as tool tip.

I prefer "Mean idle time is 7 minutes".  The question is how can I
format the text?

Paul Spencer