As @chaley said, it would help if you posted what you used as the template and the column definition.
For what it may be worth, here's my variant which gives hours, minutes, seconds:
Code:
program:
total = $#kobo_time_spent_reading;
hours = floor(total/3600);
minutes = floor(mod(total, 3600)/60);
seconds = mod(total, 60);
def format(v, str):
if v == 0 then return '' fi;
return v & ' ' & str & ' '
fed;
format(hours, 'hr') & format(minutes, 'min') & format(seconds, 'sec')