I am little bit confused about below clause of API-610 :

"As per API-610,10th edition, Unless otherwise specified, vertically suspended, double-casing, integral gear-driven (type OH6) and
horizontal multistage pumps (pumps with three or more stages) may be designed for dual pressure ratings. If
specified, suction regions shall be designed for the same MAWP as the discharge section."

I request someone to clarify the meaning of dual pressur ratings

Thanks in advance