Comparison between the prompt fluence measured in the 1 keV−10 MeV energy range and the upper limit to the 30 MeV−3 GeV fluence for the 28 events with well known prompt spectral properties. The fluence upper limit is derived under different assumptions: i) extrapolation of the prompt spectrum (yellow circles); ii) power law extra component with spectral index β = 1.8 (blue stars); and iii) power law extra component with spectral index β = 1.1 (green squares). The red diamonds are the four GRB detected by AGILE GRID.