In the first case,the black guinea pig with the genotype (BB) was quite dominant while the albino guinea pig with the genotype (bb) was recessive. Thus the dominant Gene masked the recessive Gene. The offsprings all had the genotype (Bb)
On the other hand,the second black guinea pig was also dominant but not totally because the genotype of the albino guinea pig was evident in some of the offsprings,thus the genotypes were as follows;
The black guinea pig (Bb),albino guinea pig (bb), Seven of the offsprings (Bb), the other five offsprings (bb)