We report on the experimental investigation of two types of crossover in the ordered state near the spin-flop (SF) multicritical point in the orthorhombic antiferromagnet, GdAlO3. (a) The magnetization discontinuity, ΔM (t), at the SF transition increases with power β̃=0.88±0.02 close to the SF multicritical point. Close to a critcal edge point of the SF transition shelf, however, β̃≈0.32. The bicritical-critical crossover extends over several orders of magnitude. (b) The SF transition shelf was mapped out for different directions of H ⊥. The resulting tetracritical point-bicritical line crossover appears to be rather complicated and the experimental results are not yet well understood.