I had to look that up. A 747's max fuel capacity was 63,705 US gal according to [https://en.wikipedia.org/wiki/Boeing_747] and jet fuel is around 3.25kg per gallon, so ballpark of 207,000 kg or 207 metric tons could go into the biggest 747s. 7 metric tonnes is about 2,150 gallons.

Interesting stat. Isn't a lot, but it sorta is, too.

"not so bad" is relative: It's two flights of a spacex dragon 2 launcher: 3,307 kg (7,291 lb) to ISS

https://en.wikipedia.org/wiki/SpaceX_Dragon_2

the point is that discarding lumps of metal in space is not wasteful, since it would require much more material brought into orbit to make them useful than to replace them if discarded.