the OP wants to know how many Mandos were Neo-Crusaders, and a lot of Mandos who joined during the campaign weren't Neo-Crusaders, meaning that Neo-Crusader numbers are most likely smaller than the other part of the Mando military was
What Gratular wrote. And 50.000 is just a ridiculously small number, hardly enough to crew even a single large capital ship. Even at the start of the Mandalorian wars when the Neo-Crusaders acted more as an elite vanguard, their numbers must have been in the hundreds of thousands considering every Mandalorian unit had some Neo-Crusaders.
As the war progressed the Mandalorians were able to challenge the Republic and even win until Revan joined in with his jedi, so the number must have grown well into the millions unless the Mandalorians had a truly enormous technological advantage both on the ground and with their ships in space, which I don't think they had.