Your scouting is topped up at the economic update so you have paid for last week's scouting, and if you change it now then you will change this week's scouting, which will be reflected in the balance next week. It's a strange thing, I had the same thing happen with me and I figured it out. If you had no scouting this week, then added some next week, the balance still wouldn't change but would be reflected in the following week's balance.
I think it's kind of a bug, because obviously the figures don't add up, but it's more presentational than functional.
Hope that helps, reading it back it doesn't seem all that clear but I know what I'm trying to say.