@Elio_10_94 (21 February, 2016, 2:36 PM UTC):
Please post in English next time, or provide a translation, considering this is the English forum.

Since the difference is 300 Crystals, you may have accidentally purchased a troop recall item (Or something else), which happens to cost 300 Crystals. (The troop recall item is a little more difficult to check for since there isn't any obvious lasting effect; But check your sector to see if there are any unbunkered troops you believe should have been raiding, etc., and didn't have any report)

If this isn't the case, contact the Help and Support Desk with as much information as possible on the subject.