1. One who recited the blessing and counted “today is four days…” but then realized that it is day five – if he is still within the time-period oftoch k’dei dibbur(the time it takes to say the words,“Shalom alecha Mori veRabi”), he should immediately correct himself and say “five days” etc. and he does not have to repeat the wordhayom, “today is.” But if it is aftertoch k’dei dibbur, some authorities maintain that he must recite the blessing again and count correctly, while others say that as long as he did not do or say anything extraneous since reciting the blessing, he should count without reciting a new blessing(Shulchan Aruch, Mishnah Berurah and Kaf HaChaim 489:5).
2. Some have a custom to count again [without the blessing] after the morning prayer of Shacharisso that in case he had forgotten to count on the preceding night, he will have counted during the day, which would allow him to continue counting with a blessing on the subsequent nights of Sefiras Ha’omer(Kaf HaChaimibid.).
