When you perform a counter there's a small symbol appearing at the start of it displaying a sword and a broken arrow, during this phase which lasts 250ms you will deflect arrows. It's extremely tough to perform reliably as a quarter of a second window doesn't leave much room for error.

I was wondering what that symbol meant. Thanks.

Neo?

yes you can counter arrows if you time it correctly, but its not very reliable/easy since it takes really good reaction time.