Under the integrated fluorescence usually understand the area under the fluorescence spectrum. If it is compared with the integrated fluorescence of the standard (for example, when measuring the quantum yield), one speaks about the relative integrated fluorescence. A comparison will be correct if the fluorescence spectra measurements were performed under the same conditions of excitation and registration. When calculating the relative integrated fluorescence, the full fluorescence spectra must be compared (intensity at the edges of spectrum bands should drop to zero). When the attenuator is used, it is necessary to take this into account.

Thanks Valdimir

https://www.perkinelmer.com/lab-solutions/resources/docs/APP_Determination_of_Relative_FluorescenceQuantum_Yields_using_FL6500_Fluorescence_Spect.pdf

If you are familiar and currently using the Origin lab software, this option is readily available and you can perform easily.