The way casualty calculations worked in Alexander's camp was quite simple.
Each of the ten squad captains would report his losses to his sergeant (100-man leader).
Then the tally of the 6 sergeants would be passed on to the captain (600-man leader).
The number of 10 such captains would reach the legion commander, until finally, each legion commander's number would reach Menes.
And according to the numbers submitted to him, Alexander had lost 394 dead, and 1193 really wounded.
The point of the use of the word 'Really wounded' was used because many more were shot and pierced by arrows but had no fatal or life-threatening injuries.
Such men were soon discharged from the medical clinic and so not calculated in the final tally.
So in total Alexander had actually lost around 1,500 men as dead and wounded, all who would not be available for combat any time soon, and many perhaps never.
1,500 out of 42,000 might sound like a small number, but it was actually huge.