Whenever I use crossover of 3 candle to 4 candle in 20 mins graph strangely alert generated before candle close clarify?

Algos, strategies, code
1

i was trading in crude and strangely so many signals generated without completion of 20 mins candle?

my strategy was buy when EMA 3 > EMA 4 in 20 mins candle and sell when reverse occure!!

​plz clarify

2

if you want alerts only after the close of candle   "tick mark at "  alert at end of candle  as shown in screen