Can you delete the transaction and then manually enter it, correctly?
When did you actually purchase these shares?And has there been a Stock Split 2:1 since the original purchase?
When you say you get 200, does the transaction change to 200 or is it your total holdings that change to 200? Go to Edit > Preferences > Investment Transactions and make sure "Show hidden transactions" is checked. Perhaps you have a hidden Placeholder that is adjusting your share balance.