As long as the encrypted output amounts you create is equal to the sum of the inputs that are being spent (which include an output for the recipient and a change output back to yourself and the unencrypted transaction fee), then you have a legitimate transaction and know no Monero is being created out of thin air. Pedersen commitments mean that the sums can be verified as being equal, but the Monero value of each of the sums and the Monero value of the inputs and outputs individually are undeterminable.
