Change
$credit_msg = __('You don't have enough to promote . Buy some credit.', 'payment_pro');
to
$credit_msg = __('You don\'t have enough to promote . Buy some credit.', 'payment_pro');
Forr the amounts, just multiply by 1000000, for example
$wallet = ModelPaymentPro::newInstance()->getWallet(osc_logged_user_id());
if(isset($wallet['i_amount']) && $wallet['i_amount'] > 4000000) {
$credit_msg = sprintf(__('Top up your credit [Balance:%s]', 'payment_pro'), osc_format_price($wallet['i_amount'], payment_pro_currency()));
} elseif(isset($wallet['i_amount']) && $wallet['i_amount'] > 0 && $wallet['i_amount'] < 5000000) {
$credit_msg = __('You don'\t have enough to promote . Buy some credit.', 'payment_pro');
} else {
$credit_msg = __('Your wallet is empty. Buy some credit.', 'payment_pro');
}