Material costing

I think i have misinterpreted a sentence- " the lower the inventory level we want, the higher the cost to carry, the better." This is what i have found written in a few books, kindly explain what's the meaning?

2nd question is- while computing total carrying cost i don't understand what is the logic behind dividing the number of items supplied in one order by 2 & then multiplying it by carrying cost p.u  p.a...what i mean is why don't we simply multiply the total number of units supplied p.a by carrying cost p.u  p.a?

the reason behind to divide ordering quantity by 2 . here avg quantity of stock is taken since we dont hold throught out the peroid .