Question How does one determine the Y-dna haplogroup for an individual?

[Moe]

Here is the Y-SNP calls for Barcin 31 https://genetiker.wordpress.com/y-snp-calls-for-barcin-31/.

According to the link, Barcin 31 is positive for A00-FGC27424/YP3511, A00-M8129, A0-T-YP1873, B-M8633-M182-M150-M6473, G-P287-P15-L1259-L30-CTS1180/PF3259/M3244, IJK-PF3500/M2696, J-PF4513, Q-L274-L472-F1096-M25-L712-L715-YP836, R1b-L278-L389-P297-M269-PF5462 and so on but eventually "The calls show that Barcın 31 belonged to Y haplogroup G2a2b-L30*".

Is it correct if we assigned this individual as A00, A0-T, basal J or any of the Y-dna haplogroups above because the individual have SNPs belong to other Y-dna haplogroups? If it is not, why?

 

[Gao1111]

SNP testing

 

[Moe]

SNP testing

Yeah but how? How do they do the testing and how do they confirm the Y-dna haplogroup?

For example, why did they assigned Y-dna haplogroup G for Barcin 31 while at the same time Barcin 31 is also positive for SNPs that defined other Y-dna haplogroups?