src/Money/DataMapper/Data/Money/Abstracts/TransactionAbstract.php
public function setAmount($amount)
    {
        $amount = (float) $amount;

        if ($this->exists() && $this->amount !== $amount) {
            $this->updated['amount'] = true;
        }

        $this->amount = $amount;

        return $this;
    }
public function setAmount($amount)
    {
        $amount = (float) $amount;

        if ($this->exists() && $this->amount !== $amount) {
            $this->updated['amount'] = true;
        }

        $this->amount = $amount;

        return $this;
    }
Set value for field "transaction_amount"

@param  float $amount
@return $this