Photo: La Fuite de Pompée après la défaite de Pharsale. Courtesy of Wikipedia.
Caesar had about 22,000 men and Pompey had twice that, but Caesar still won, losing only about 250 men. 24,000 of Pompey's men surrendered; the rest died or fled the battle.
Julius Caesar describes the Battle of Pharsalus in his Civil War Commentaries, and the Silver Age Latin poet and nephew of Seneca, Lucan wrote about it in his Pharsalia [English translation].
Note that if it seems a lot more battles were waged at this time of year than earlier, there was a limited regular battle season. The battle season would have been winding down. To make it just a bit more interesting/confusing, The Battle of Pharsalus was early June on the Julian Calendar.