Looking at generic products of Madopar (levodopa plus benserazide) which is similar to Sinemet (levodopa plus carbidopa), a group of researchers have found similar deviations in the weights of the active ingredients [1]:

"Each of the seven generic products had one or two parameters outside the specifications. Deviations for the active ingredients ranged from +8.4% (benserazide) to −7.6% (levodopa) in two tablet formulations."

John

Reference:

[1] "Pharmaceutical quality of seven generic Levodopa/Benserazide products compared with original Madopar/ Prolopa"
Urs E Gasser1, Anton Fischer , Jan P Timmermans and Isabelle Arnet
BMC Pharmacology and Toxicology 2013, https://bmcpharmacoltoxicol.biomedce...050-6511-14-24