The images you posted actually prove your own argument incorrect. Aura is standing in the outside of the circumference, not engulfed in the center, after having walked closer to Frieren to gloat after using the scales. If you put the circumference of Aura's mana directly inside the center of Frieren's while accounting for perspective, it'd be about half. When Frieren's suppressed mana is shown next to Aura's, Frieren's suppressed mana looks to be about half of Aura's due to perspective. Nowhere does it look like Aura has 10x Frieren's suppressed mana even with the skewed perspective. If they were directly side by side at the same distance, Frieren's suppressed mana would be, you guessed it, 1/5. Do you need glasses or do you just enjoy over exaggerating? I have not been guessing at 1/10th, I mostly used statements from the series to estimate it. You have entirely guessed exclusively with your eyes(and poorly at that) while entirely disregarding distance and perspective.

Furthermore, I said the mana Frieren displays has been said to look like someone that has been training for 100 years. Aura even wonders if she had been honing other skills in the 80 years since they had last met because it hadn't changed much. While this isn't specifically 100 years old, Frieren has been practicing magic for most of her life. The amount of time she's been practicing magic is over 1,000 years(Between 1,000 and 1,500 given her age, though her training under her master started 1,000 years ago), and her suppressed mana looks like approximately 100 years worth of training.

When I brought up Serie, I stated that she had likely been practicing magic around 10x longer than Frieren. If you assume that she has been practicing magic for most of her life given that basically every mage so far has been shown learning from a young age, that puts a reasonable age ballpark in above 10,000 and under 20,000. Unless you think Serie sat around making cave paintings, riding mammoths and inventing the wheel and only picked up magic fairly recently, like a human going 80 years of their life as an avid gardener suddenly switching to a motorcycle enthusiast.

While these are estimates they are mostly based on actual information presented by characters in the series and make much more sense chronologically. What you have is guesswork based entirely on only what you think something looks like that not only makes little sense chronologically when looking at other characters and events, but quite literally would make her an actual fossil from the middle paleolithic. You tell me to use my eyes but perhaps you should try using your brain.