Normaly when inputting commands in a command block for the "effect" command I would put "/effect @p minecraft:speed 10 2"
and it would have the speed of "2" as it is there.

However when I put the command in and activated it it gave me speed three not two.

Steps to Reproduce:
1. Place command block on block Place lever on command block.
2. Change it to a repeat command block (leave the rest normal).
3. Input command "/effect @p minecraft:speed 10 2" then activate and check inventory.