The properties of superconducting plates with a thickness of the order of the coherence length ξ have been investigated by numerically solving the system of one-dimensional Ginzburg-Landau equations. The equations have been solved using boundary conditions of the general form for the order parameter, which makes it possible to take into account the influence of the boundaries of the plate on its superconducting properties. The behavior of the critical current and critical magnetic field as a function of external parameters has been analyzed. It has been shown that the inclusion of the influence of the boundary in the calculations leads to results that are in better agreement with the experimental data.