i have a 2007 chevrolet impala ss everytime i check my transmission fluid with...

Showing full when the engine off is misleading. The fluid is not being pump thru the transmission and pools at the bottom of the pan. The reason it shows full when you first full it out while it is running is because you have not wiped it from when it was off. You need to drive for about 30 minutes to warm the fluid up and then pull the stick and wipe and then check your level. A transmission can run and not slip if it is missing some fluid but it is not safe to do. If it is not showing on the stick pour about a half a pint in and check it again. If you have not had it flushed or changed in over 30,000 miles you should take it in and have it done. Transmission fluid needs to be changed like your engine oil.

agreed.
but one exception, and it's not really pertinent to your fluid level issue.
FYI,
do not flush the trans. causes more issues on some trans than it *tries* to solve.
the idea is flushing out particulate matter. if particulate matter is trapped behind a seal or pump, to flush that, the seals would have to be bad. leaking in the first place. if particles came from a component behind a seal, then flushing may force it past the seal. compromising the seal. it can get micro cuts. like what maybe sand paper would do to a seal.

only way to get the results a flush job *tries* to accomplish, is to dis-assemble, tear down, clean, inspect. and a flush job will not flush a converter. it has a large volume low spot. can't be flushed.
and all that will cost more than a re-manned trans.