If Oanda recognizes the 5 lots as 5 contracts, then the live lot amount was obviously 1, not 0.1. Change it to 1 in the asset list and make sure that the size is then correct in test and trade mode. And check also with Oanda why they told you it was 0.1 when in fact it was 1. Maybe your account was not yet updated to 0.1 or that server returned a wrong value.