First let's define some terms.
Your accrued benefit is a monthly benefit payable at your normal retirement age (usually 65). It is usually a life-only benefit but may have a number of years guaranteed or may have a survivor piece. It is defined by a plan formula (ie, it is a defined benefit).
A lump sum is how much that accrued benefit is worth right now. Lump sums are based on applicable interest rates and mortality tables specified by the IRS (interest rates are released monthly, mortality annually). Your plan can either use the same interest rates for a whole year, or they can use new ones each month.
Affecting your lump sum is whether your accrued benefit is payable now (immediately, you are age 65), or later (deferred, you are now age 30).
For example, instead of being paid an annuity assume you are paid just one payment of $1,000 on your 65th birthday. The lump sum of that for a 65 year old would be $1,000 since there would be no interest discount, and no chance of dying before payment. For a 30 year old, at 4% interest the lump sum would be about $237 (including mortality discount). At age 36 the lump sum is $246. So the lump sum will get bigger just because you get older.
Very important is the interest discount. At age 30 in the example, 2% interest would produce a $467 lump sum. And at 6% $122. The bigger the rate, the smaller the lump sum because interest helps an amount now grow bigger in the future.
To complicate things, since 2008 the IRS bases lump sums on 3 different interest rates. The monthy annuity payments made within 5 years of the lump sum date use the 1st rate, past 5 and within 20 years use the 2nd rate, and past that use the 3rd rate.
Since you are age 30, all of your monthly annuity payments would be made after 20 years, so that makes it simple since we'll only have to look at the 3rd rate. When you reach age 45 the 2nd rate will kick in.
Here is the table of interest rates published by the IRS:
You'll find your rates above on the 2013 line for Aug-12. That means your lump sum is being made in 2013 and it is being based on the month August 2012. Most likely your plan will use the same rates for its entire plan year. But what is your plan year? If it is the calendar year, then you would have a 5 month lookback for the rates. But if is a September to August plan year with a 1 month lookback, the rates would have changed between August and September. Your August lump sum would be based on 4.52%, your September on would be based on 5.58% (see the All line for Aug-13).
For comparison, a 30 year old with a $100 annuity payable at age 65 would have a lump sum value of $3,011 at 4.52%, but a lump sum value of $1,931 at 5.58%.
The change in your accrued benefit by month will obviously have some impact on the lump sum value, but not as much as the change in interest rates if there is one.
The amount they actually contribute to the plan has nothing to do with the value of the lump sum though.