There is a problem in Scratch 2 where you cannot easily differentiate between variables that are global (shared by all sprites) and those that are local to the current sprite.
In the old version these were separated by a dividing line.
The screenshot below shows the three types of variable that are available in the online version.
Cloud variables have a cloud icon to differentiate them. Local and global variables look the same.
The workaround which can be seen in the screenshot is to make the variables visible temporarily on the screen. Then local variables are prefixed by the name of the sprite of which they are members.