  The main asteroid belt (MAB) is known to be primarily composed of objects
from two distinct taxonomic classes, generically defined here as S- and
C-complex. The former probably originated from the inner solar system (interior
to Jupiter's orbit), while the latter probably from the outer solar system.
Following this definition, (4) Vesta, a V-type residing in the inner MAB (a <
2.5 au), is the sole D > 500 km object akin to S-complex that potentially
formed in-situ. This provides a useful constraint on the number of D > 500 km
bodies that could have formed, or grown, within the primordial MAB. In this
work we numerically simulate the accretion of objects in the MAB region during
the time when gas in the protoplanetary disk still existed, while assuming
different MAB primordial masses. We then accounted for the depletion of that
population happening after gas disk dispersal. In our analysis, we subdivided
the MAB into five sub-regions and showed that the depletion factor varies
throughout the MAB. This results in uneven radial- and size-dependent depletion
of the MAB. We show that the MAB primordial mass has to be $\lesssim$
2.14$\times$10$^{-3}$ Earth masses. Larger primordial masses would lead to the
accretion of tens-to-thousands of S-complex objects with D > 500 km in the MAB.
Such large objects would survive depletion even in the outer sub-regions (a >
2.5 au), thus being inconsistent with observations. Our results also indicate
that S-complex objects with D > 200-300 km, including (4) Vesta, are likely to
be terrestrial planetesimals implanted into the MAB rather than formed in-situ.
