We use the method of the Time Weighted Return to calculate the return on your portfolio.
It can be difficult to determine how much money was earned on a portfolio when there are multiple deposits and withdrawals made over time. Investors can't simply subtract the beginning balance, after the initial deposit, from the ending balance since the ending balance reflects both the rate of return on the investments and any deposits or withdrawals during the time invested in the fund.
When using Time Weighted Return it might occur, that the absolute amount of your return is negative, while the relative amount is positive. If you had a good return in percentage on a small investment, both is positive. But if you then transfer a large reinvestment in the next month which has negative performance, it will impact the absolute amount more than the return in percentage.