I noticed that when my Mutual Fund is performing negatively, not only my NAV (Net Asset Value) decreases (which is understandable), but also my total number of units (that I bought) goes down. However, when the Mutual Fund is performing positive, my NAV increases, but the total number of units remains the same. Why so?
Depending on the fund you have subscribed to, there are some maintenance fees deducted by the broker, and for this purpose, some units are sold.
Edit: Clarifying the various comments, I guess everyone is on same page and saying the same thing a bit differently. The funds could be managed by a broker and there is a charge separate to the fund house. This is more often seen in ULIPS, Retirement Funds etc.