Where? At court, he stated "I would have said, in fact, 3 minutes was the total of the two conversations." He was immediately asked to confirm this, and said "Yes".
The two calls you have referred to are West's call to Bonnett at 03.26 and his call to Witham at 03.30. The basic point people seem to overlook is that if Jeremy called West at 03.36, West must have made those two calls after putting Nevill on hold and not Jeremy. So arguments based on the length of those earlier calls have no relevance to the question as to when Jeremy left Goldhanger or how fast he drove, if he called the police at 03:36.
If Jeremy called at 03.36 and West spoke to him for a minute before calling Witham, as is suggested by Myall's note which times West's call at 03.37, there would only be this one call before West got back to Jeremy, so the time he was on hold may have been no more than 3 minutes.
So Jeremy could have left for Whitehouse farm at around 03.40.