In order to have it appear in a single chart you need to get the travel time intot he report twice, once as travel with the table time value and once as travel (billable) with time value*.5.If you dont need these to appear in the cahrt you can use two formulas to get seperate values.
billable values would be something like
if field in (service,contract) then value else if field=travel then value*.5 else 0
for travel only
then if field=travel then value
for lunch
if field = lunch then value
now you can sum each of these and get 3 seperate values for billing lunch and travel
will that work?