Prior to the creation of that transaction, the address 1fMDuZm16nWzjzfwC6ynC99Vq4MMYtXuF had 4 previously received and unspent outputs:
This adds up to a total of
0.022 BTC in unspent outputs received at that address.
All 4 of these outputs were spent in the transaction that you posted, (along with outputs received at 4 other addresses). The sum of all outputs funding the transaction was 0.054405 BTC. That transaction sent 0.05 BTC to 15yMPzHCofjfBux9s4gYFux9mP5UL66FuG, paid a 0.0002 BTC fee, and
0.004205 BTC in "change" was sent back to address 1fMDuZm16nWzjzfwC6ynC99Vq4MMYtXuF.
0.022 BTC spent - 0.004205 BTC received in change = a net change of 0.017795 BTC spent