During a standard penetration test (SPT) in a cohesionless soil deposit, the sampler is driven 450 mm total using a 63.5 kg hammer with a free fall of 760 mm. The recorded N-value (blow count for the last 300 mm of penetration) is 28. The measured effective overburden pressure at the test depth is 140 kPa and the unit weight of soil is 18 kN/m³. According to commonly used correlations for SPT in sand, which of the following is the most appropriate correction to apply to the measured N-value before using it for liquefaction or relative density correlations?