The ICARUS liquid argon TPC, currently placed at Fermilab, is collecting data since 2022 exposed to Booster Neutrino Beam (BNB) and NuMi off-axis beam within the SBN program. A light detection system, based on PMTs deployed behind the TPC wire chambers, is in place to detect vacuum ultraviolet photons produced by ionizing particles in liquid argon. This system is fundamental for the detector operation, providing an efficient trigger and contributing to the 3D reconstruction of events. Moreover, since the TPC is exposed to a huge flux of cosmic rays due to its operations at shallow depths, the light detection system allows for the time reconstruction of events, contributing to the identification and to the selection of neutrino interactions within the beam spill gates. This contribution focuses on the light signals study devoted to improve the agreement between data and MC. In particular, the MC is tuned on data-basis modifying the light simulation’s parameters related to the gain and to the quantum efficiency.