[GAP Forum] I am puzzled by the function DihedralGroup(n)!

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Dear Forum,Dear Everyone:
As we all know, a dihedral group  $D_{2n}$ is generated by two elements $a$ and $b$ such that $a^n=1,b^2=1$ and $aba=b$. Hence $D_{2n}$ consists of  $2n$ elements. However the following statements puzzle me:
gap>d8:=DihedralGroup(8);
<pc group of size 8 with 3 generators>
gap>d10:=DihedralGroup(10);
<pc group of size 10 with 2 generators>
The first statement implies that d8 has 3 generators. The second statement implies that d10 has 2 elements. WHY?
Best wishes!