10,000 is a really really low number compared realistically, in modern times especially for a short period, it may look like a lot of people but if we go back to ancient times for example lets take late republic period of rome, there in caesar's campaign its said a million people were killed and a further million were enslaved, later in time of emperor augustus rome lost full 3 legions in germanica
even if we go more into past lets say battle of cannae rome against hannibal on extreme estimate rome lost 70,000 men on a single day and even on lower estimate it easily crossess 40,000 mark,
and the emperor bloody finished the conflict with only 10,000 dead, that guy is a genius and probably the best kind of emperor you can get for that time