Fix changeBloodType (#590)

**When merged this pull request will:**
- Fixes changeBloodType to work

### IMPORTANT

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are read, understood and applied.
- Title of this PR uses our standard template `Component -
Add|Fix|Improve|Change|Make|Remove {changes}`.

addons/zeus/functions/fnc_ui_changeBloodType.sqf

@@ -116,7 +116,7 @@ private _fnc_onConfirm = {
     private _curBloodVol = GET_BLOOD_VOLUME_LITERS(_unit);
     private _sliderValue = sliderPosition (_display displayCtrl 26423);
     _sliderValue = parseNumber (_sliderValue toFixed 2);
-    REDUCE_TOTAL_BLOOD_VOLUME(_unit,_sliderVolume); 
+    REDUCE_TOTAL_BLOOD_VOLUME(_unit,((_curBloodVol - _sliderValue) * 1000)); 
 };
 
 _display displayAddEventHandler ["Unload", _fnc_onUnload];