for any talend component look under outline tab under the left side workspace pane at the bottom. this lists down the properties available via global variables for that component. Some properties like count of records inserted by output components are only available once the component is executed completely (After).
for your case you can try directly using ((Integer)globalMap.get("tFixedFlowInput_1_NB_LINE")) which gives number of lines (after) given by tFixedFlowInput.