VAR has made four mistakes so far during the Premier League season, referees' chief Mike Riley has admitted.
The examples, which include Fabian Schar's equaliser for Newcastle against Watford and Leicester midfielder Youri Tielemans' apparent stamp on Bournemouth's Callum Wilson, were discussed in Thursday's meeting of Premier League shareholders.
The other two errors were the referee's decision not to award Manchester City a penalty when Jefferson Lerma stood on David Silva's foot in the Bournemouth box and a decision not to give West Ham a penalty when Sebastien Haller was brought down by Norwich's Tom Trybull.
VAR in the Premier League
227 - Incidents checked by VAR
6 - On-field decisions changed
10 - Decisions that should have been overturned
Riley, the managing director of the elite refereeing body, PGMOL said: "We are learning as we go along and we are constantly improving.
"Out of the four match rounds, there have been some really good examples where we have intervened. There have been six incidents where VAR has advised the referee and we have got a better decision as a result.
"There were four incidents where VAR didn't intervene and had they done, we would have a better understanding of the role VAR plays in the game. [The mistakes] are all about the judgement of VAR and the process that we adopt.
"These are examples where VAR could have had a benefit and intervened to help the referee on the day."
When pressed on why those mistakes were made, Riley added: "A combination of factors. That is the fascinating thing as this project evolves, we are constantly learning.