[Laurent Rizzotti]

My understanding of this:

According to recent information one tanker of 15,000 tons (in spite of her degaussing equipment) and another tanker of 6,000 tons were lost through striking mines (aerial) off St* Nazaire. This shows that, despite all defense measures, aerial mines are still effective and confirms the need of continuing to use them as much as possible.

is that the Germans learned in early July that two ALLIED tankers were lost to aerial mines off Saint-Nazaire, probably during June 1940, and so they were still efficient despite Allied counter-measures (like degaussing) and their use should continue.

Then the 15000-ton tanker will be the French tanker Palmyre (14715 tons) sunk on 17 June 1940 by a mine near Saint-Nazaire. I can't find another loss to mines in the same area, but the passenger ship Mexique (11953 tons) was sunk on the 18th off Le Verdon, more south.