Hi Boscoe
Lilybell has provided the essence of the program. Boscoe also asked the value paid & about the year 1912.
I've only seen write-ups that indicate the program ran from 1890 - 1906, though have relatives that sailed in 1909 marked as British Bonus Allowed, so it obviously continued after that time (though perhaps modified

.)
"British Bonus" was a subtle marketing tool used by the Canadian government as the laws of the time in many European countries forbade open encouragement of immigration by any foreign country.
As Lilybell indicated, it served to encourage steamship booking agents to recruit desirable settlers (farmer, domestics, etc.); first it centered on recruiting immigrants to western Canada; later was also provided to those settling in Ontario.
It originally included:
1. To pay a limited amount, not exceeding in any case $50.00, to the class of "returned men" (not exceeding fifty) to Europe toward recouping their expenses on sufficient proof furnished of success in bringing immigrants to Canada.
2. To pay a bonus to Steamship Agents in the United Kingdom, of $5.00 for each adult settler on land, of 18 years and over, on certificate of booking and shipping such settler to Manitoba, the Northwest Territories of British Columbia, and, on certificate of a Dominion Lands Agent, to be furnished as proof of such settler.
3. To pay a bonus of $10.00 to each homesteader, the head of a family, and $5.00 for each member of such family at the adult age of 12 years and over, with an additional $5.00 to any such member of a family who might within six months after arrival in Canada become a homesteader on settlement on land in Manitoba, the Northwest Territories of British Columbia, proof being furnished of such settlement by the certificate of a Dominion Lands Agent.
While the arrangement above was in place, many suggestions were received by the Department recommending that the regulations be altered so that a bonus would be payable when the immigrant arrived in Canada instead of when he took up land. I'm not sure when the change occurred, but have seen indications that it was finally agreed to pay of bonus of $1.75 on adults and half that amount on children from the British Isles arriving in Winnipeg, Manitoba.
I hope this helps.