Any changes to the frequencies of gnomAD v2.1 liftover ?

Question

[乙]

Dear community,

I tried to look for any information on their website concerning my question. I would like to know if the gnomAD v2.1 liftover version (hg38) changes the frequency for a given mutation or its annotation from the original analysis (hg19). I speculate that the only changes made are the positions of each mutation on the chromosomes.

However, as an example (randomly chosen), I downloaded the chrY and took the first mutation from both hg19 (right) and hg38 (left) and I found some differences:

And

Apart from those, all the other frequencies are similar. Can someone explain me please why are there differences such as these ?

Thank you in advance.