... Say you buy a $10,000 5-year 3.5% callable CD.
After 3 years the issuer calls it and at the time interest rates for 2-year CDs are 2%.
If the issuer had not called the CD then at the end of 5-years you would have received $11,877 [10,000*(1+3.5%)^5].
At the current interest rate of 2% that you would reinvest the call proceeds in, in order to have $11,877 at the end of two years you would need to receive $11,416 today [(11,877/(1+2%)^2].
The CD with accrued interest is currently $11,087 [($10,000*(1+3.5%)^3].
So when the CD is called the issuer pays you $10,000 principal, $1,087 of accrued interest and a $329 make-whole call penalty for a total of $11,416.
You reinvest the $11,416 for 2 years at 2% and at the end of 2 years have $11,877... the same as if the issuer had not called the CD... so you have been "made whole".