Thanks for the question -- an excuse to return to Vim Adventures for the first time in a while!  Thanks!!

I've just confirmed that it's possible to edit that text in the required keystrokes, with the keys you have now:
[![My keys collection matches yours early in Level 6.][1]][1]
[![I edited the 'asdf ' word with strokes to spare.][2]][2]

My keys collection matches yours early in Level 6, and I edited the 'asdf ' word with strokes to spare, releasing a yellow key.

Without giving too much away -- I didn't do it on the first pass through; and it really helps to approach it backwards.

I hope that helps; and if you're still stuck, I'll give a more complete answer.

  [1]: https://i.sstatic.net/QAhKG.png
  [2]: https://i.sstatic.net/wNXEb.png