DNA matches half uncle

I was wondering if anyone could answer this question I have. I have DNA match with my half uncle ( fathers side) , and I also have a half great Aunty - mother’s side. My sister has a slightly higher cM reading with the great half aunt than she does with her half uncle. 590 with half great aunt and 500 with half uncle. Shouldn’t the half uncle read higher.
I share 758cM with half uncle and 456cM with half great aunt. All very odd ?

From the The Shared cM Project 4.0 tool v4 a match of:

• 758cM between you and your half uncle has a probability of 86%.
• 456cM between you and your half great aunt has a probability of 86%.

For your sister a match of:

• 500cM between her and your half uncle has a probability of 5%.
• 590cM between her and your half great aunt has a probability of 78%.

While the half uncle and half great aunt relationships are more strongly supported for you than your sister, it is only the great uncle relationship to your sister that is other than strongly supported, but it is nevertheless supported. I think this is a case of you and your sister, by chance, receiving different amounts of your paternal grandfather's DNA.

• Thank you. It will be the latter. my sister and I are full siblings. – Cam Apr 16 at 3:26

Reason why I posted the 2nd enquiry was because my original question was never answered. I apologise for asking a 2nd time !