Hello

I was looking some music sheets i found somewhere around and i saw something that confuse me

The song comes with a pentagram showing that the notes on this section/measure are all Eighths then it should be a steady rythm of down strokes or an even series of alternate strokes, right?

But I see it comes with a strumming pattern like the one given on the typical "chord over lyrics" notation... like DDU UDU

Now, how is that pattern a line of full Eighths? it is possible or its a mistake?