How to modify the size of badges

I can’t seem to modify the size of the badges in my BuddyPress site. It is set to 100×100 by default. I have seen this from the documentation

define( 'MYCRED_BADGE_WIDTH', 50 );
define( 'MYCRED_BADGE_HEIGHT', 50 );

but it made my site show me a 500 error. How can I really modify it to look neat not too big and the whole site looks untidy. Thanks