  The extent of mixed regions around convective zones is one of the biggest
uncertainties in stellar evolution. 1D overshooting descriptions introduce a
free parameter ($f_{ov}$) that is in general not well constrained from
observations. Especially in small central convective regions the value is
highly uncertain due to its tight connection to the pressure scale height.
Long-term multi-dimensional hydrodynamic simulations can be used to study the
size of the overshooting region and the involved mixing processes. Here we show
how one can calibrate an overshooting parameter by performing 2D Maestro
simulations of Zero-Age-Main-Sequence stars ranging from $1.3$ to $3.5
M_\odot$. The simulations cover the convective cores of the stars and a large
fraction of the surrounding radiative envelope. We follow the convective flow
for at least 20 convective turnover times, while the longest simulation covers
430 turnover time scales. This allows us to study how the mixing as well as the
convective boundary evolve with time, and how the resulting entrainment can be
interpreted in terms of overshooting parameters. We find that increasing the
overshooting parameter $f_{ov}$ beyond a certain value in the initial model of
our simulations, changes the mixing behaviour completely. This result can be
used to put limits on the overshooting parameter. We find $0.010 < f_{ov} <
0.017$ to be in good agreement with our simulations of a $3.5 M_\odot$ mass
star. We also identify a diffusive mixing component due to internal gravity
waves (IGW) that is active throughout the convectively stable layer, but likely
overestimated in our simulations. Furthermore, applying our calibration method
to simulations of less massive stars suggests a need for a mass-dependent
overshooting description where the mixing in terms of the pressure scale height
is reduced for small convective cores.
