RETURN THE TWENTY FIVE

hello people!

i have a doubt concerning a song from Mungo Jerry, called "in the summertime"
in this song we have these lines:

"speed along the lane
do a turn and return the 25"

i would like to know what is this 25? is it a slang? i thought it could be the limit of velocity
but we also can understand:

"speed along the lane
do a ton or a ton and 25"

i don't know what exactly he says, but here is my doubt! thanks!