Why the shortcut is closed here
Mali has not joined the Hague Apostille Convention, and membership is exactly what makes one certificate enough between two states. An apostille from United Kingdom to Mali therefore stops short of what a receiving office needs to act on. Two stages take its place: a British certification of the signature on the sheet, and a consular stamp added here on behalf of Mali.
Signatures and seals, and nothing beyond them
Each mark on the finished paper is a narrow statement. The British stage says that the signature at the foot of the sheet belongs to somebody whose signature that office holds on record. The consular stage says that the British mark above it is authentic. Neither one comments on the contents, the accuracy of an entry, or the standing of the person who ordered the copy.
That narrowness is useful once you see it. It explains why a document with every stamp in place can still be turned down for a reason that has nothing to do with certification — a missing form, an out-of-date requirement, a name recorded differently somewhere else. The chain proves origin; it does not argue your case for you.
Where the local office fits in
For births, marriages and deaths recorded in the city, Stoke-on-Trent Register Office prints a fresh certified copy signed by a registrar, and it is that certified copy which goes into the envelope while the one at home stays put. Papers of any other kind start with their own issuer instead, and the rest of the corridor treats them identically once an official signature is on them.
Counting by the sheet
Because the British charge attaches to each document, the bill is decided before anything is posted, by how many sheets are in the pile. A consular charge follows on top and is set well away from Britain. The timing works the same way: two postal legs and one consular queue, none of which move faster because the packet happens to be a large one.