The value of the limits generated by pledged shares in Shares As Margin depends on the Quantity, Price and Haircut of the stock. 

The formula for creation of limits is as follows:

(Quantity of the stock deposited * Price of the stock) * (1 - Haircut% for the stock) 

As the price of the stocks varies daily, the corresponding limits that are created by pledging the securities also change. 

Generally, the previous day’s closing price is taken as the Valuation Price of the stock. So, if the price of the stock starts to fall, funding limits that are generated by pledging the stock decreases, vice-versa as the price of the stock increases the funding limits are also increased. Limits will also vary due to changes in haircut% of the stock. 

Whenever you take positions using Shares As Margin limits and the value of the limits starts to fall. The positions taken using those Shares As Margin limits may get squared off due to lack of sufficient margins. 

Therefore, whenever you have taken F&O and Equity positions on the basis of limits arising from Shares As Margin, you are advised to track the prices of stocks and ensure that sufficient margin is always available.

PFB an example for your reference:

Before Pledged shares value decrease

Pledged Securities- 1000

Current Allocation- 1000

Free Securities- 0

MTF IM- 1000

After Pledged shares value decrease

Pledged Securities- 900

Current Allocation- 900

MTF IM- 900 (1000-100)

Free Securities- -100

In such cases, the MTF position will get squared off as sufficient free limits are not available.