Jolteon's speed can go as low as 296, while being as high as 359. An agility times the speed by 2. But the thing you may be talking about is that Jolteon and all other baton passers only pass the agility, not the speed.
So lets do this:
Jolteon has 300 speed. Agility is used making it 600.
Jolteon then baton passes it to someone with 100 speed.
That one with 100 speed now becomes 200.
To summarise, what baton passing does is pass the boosts not the stat.
Black code: 3611 3351 1490 √-1