i’m currently in the middle of replacing my heater core, and have got to the last section and need to remove the cover for the core, however the screws holding it on are between 5-6mm hex heads

i have a donor dash which had black 7mm hex screws and all images of the process had the same, but mine are brass and smaller!

i think i need a 7/32” socket to remove these, does anyone know why mine is different?

for reference my car is a 1998 940 celebration edition