It's the actual shipping rate (charge) for the weight bracket (from/to)... Assuming you don't check "Use percentage:".
What's confusing is that the form shows the "Charge percentage (of subtotal):" even when the "Use percentage:" is not checked. You really should only enter an amount in either the "Charge percentage (of subtotal):" (when Use.. is checked), or in "Charge amount" (when Use... is not checked).
If using "Charge percentage (of subtotal):", the weight determines the % to use, but the % is applied to the sub total $ amount.
If "Use percentage:" is not checked, the " minimum charge option" would be the charge you set on the brackets - e.g. create a bracket 0 .. n, and that charge will be the minimum.
Here's the actual calculation (abbreviated)
if (shippingByWeightRecord.UsePercentage)
shippingTotal = subTotal * (shippingByWeightRecord.ShippingChargePercentage / 100)
else
{
if (_shippingByWeightSettings.CalculatePerWeightUnit)
shippingTotal = shippingByWeightRecord.ShippingChargeAmount * weight;
else
shippingTotal = shippingByWeightRecord.ShippingChargeAmount;
}
I've posted this before, but I'll repeat here... - there's an (accidentally) hidden feature:
The CalculatePerWeightUnit setting is not visible in the config page, yet it is a Setting in the db.
By default it's False which means when the weight is in the range, the shipping charge itself is applied (the else case):
if (_shippingByWeightSettings.CalculatePerWeightUnit)
shippingTotal = shippingByWeightRecord.ShippingChargeAmount * weight;
else
shippingTotal = shippingByWeightRecord.ShippingChargeAmount;
Workaround to not having in config page is that you can change the setting in Configuration > Settings > All Settings:
shippingbyweightsettings.calculateperweightunit False
shippingbyweightsettings.limitmethodstocreated True
You might be interested in
https://www.nopcommerce.com/boards/t/13776/shipping-director-plugin-beta1-released.aspx