Shadow price/Limiting factors

Hi john, Would appreciate your guidance made on the statement made in bpp book, ''The shadow price of a resource is its internal opportunity cost. This is the marginal contribution towards fixed costs and profit that can be earned for each unit of the limiting factor that is available'' How is shadow price an opportunity cost ? does it mean that, for example- the company has 2 options,1) to increase contribution by creating 1 additional unit of the limiting factor and 2) losing the extra contribution that could be earned by not creating any additional unit of the limiting factor. And so in both of the options above the contribution earned/ lost is the shadow price.