The last figure represents the percentage of potassium or potash in the bag, this varies from 1-10. Wood ashes contain up to 70 percent calcium carbonate, as well as potassium, phosphorus, and many trace elements. Other ways to replace calcium and potash from lime is with crushed eggshells, bonemeal, or wood ashes. Wood ashes are very alkaline, and since they have a very fine particle size, they act as a fast-acting liming material. Lime and ashes raise the pH of the soil, so use wood ashes in moderation to avoid those high pH levels.
Microorganism are unable to break down organic matter in high alkaline soils.
Some plants find it difficult to take up nutrients when the soil has a higher pH. These are all reasons not to spread ashes heavily in one spot. Care must be taken not to put ashes where acid loving plants are located, or where you plan to grow plants that like soil on the acid side like potatoes, blueberries and azaleas. Ashes may be used in a flower bed or new area to be planted if the pH is to high. The most important thing, prior to any adding anything to the soil is to have the soil tested to see what the pH is. If liming is required, limit applications of ashes to 10 pounds per 100 square feet.