diff --git a/src/cal_tools/agipdlib.py b/src/cal_tools/agipdlib.py
index e52e1a007abac353a54d73de85b8c2e52e651ea5..2f4046a6c88193319545e9102b7d704a57cae8fc 100644
--- a/src/cal_tools/agipdlib.py
+++ b/src/cal_tools/agipdlib.py
@@ -86,8 +86,9 @@ class AgipdCtrl:
         ncell = self._get_num_cells_ctrl()
         if ncell is not None:
             return ncell
-        # In case of data filtering at DAQ, this function produces
-        # wrong value.
+        # The method implemented in this function doesn't suit for filtered
+        # data. If DAQ filters data and the last cell is removed, the
+        # function returns wrong value
         return self._get_num_cells_instr()
 
     def _get_acq_rate_ctrl(self) -> Optional[float]: