The illustrated rate is an assumption about the insurer's investment fund, not the yearly return on what you pay. You pay premiums over time, part of each premium covers insurance and costs, and only the guaranteed part is a promise. The yearly return on your own payments is usually lower than the headline illustrated rate.
Two different percentages
One is the rate at which the insurer illustrates its fund growing, such as 4.25% in the higher case. The other is the yearly return on your own premiums, taking into account the dates you pay them and what the policy finally pays out. They are not the same number, and the second is the one that tells you what you earn.
A made-up example
In the made-up example on the analyser, a 10-year plan illustrated at the lower and higher rates works out to roughly 0.9% to 1.9% a year on the premiums paid, and about 0.3% a year on the guaranteed amount alone. These are not real figures, but they show the size of the gap between an illustrated fund rate and a yearly return on premiums.
How to check your own plan
Upload your illustration to the analyser. It reads the dated premiums and the payout, works out the yearly return (the internal rate of return) on each, and cross-checks it against the yield your insurer prints, when there is one.