Give this a try:
=if(COUNTIFS('TRADE LOG'!P:P,"L",'TRADE LOG'!B:B,">="&DATE(2021,2,1),'TRADE LOG'!B:B,"<="&DATE(2021,2,28))=0,"",COUNTIFS('TRADE LOG'!P:P,"L",'TRADE LOG'!B:B,">="&DATE(2021,2,1),'TRADE LOG'!B:B,"<="&DATE(2021,2,28)))
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…