Custom clearing MIRO

All Experts,

In Purchase order i have maintained total 20 conditions out of which 7 are custom conditions.

Now while doing custom clearing miro, only those 7 conditions ( JCDB,JCV1,JECV,J1CV,JEDB,JADC,JSDB ) are displayed ?

Why and How ?

And every time while creating miro system asks for company code, Why ?

Thanks & Regards,

Sandeep