Drivers will reportedly be charged for each crossing, not for a return journey.
Other drafted signs include information instructing a driver about the final exit to take before the tunnels' charge kicks in.
TfL insist no decision had been made, adding that the figures were just “placeholders” used to illustrate the design layout of the signs.
The Silvertown tunnel, which Sadiq Khan oversees, does not yet have a set figure to use the tunnel.
The toll amount is not expected to be announced until much closer to the opening date.
Drivers will have to pay the fee online rather than at a toll booth.
The Transport Secretary, Mark Harper has approved a request from Transport for London (TfL) to install road signs
A spokesperson for the Stop the Silvertown tunnel, which spotted the DfT approval of the road signs, told the Evening Standard: “Ulez expansion faced fierce resistance - but it also had political support, because it was intended to reduce exisiting pollution.
“The proposed new toll on the Blackwall tunnel brings no benefits at all; it is there only to remove the new, extra traffic, congestion, pollution and CO2 emissions that will be generated by the Mayor’s own Silvertown tunnel."
A TfL spokesperson said: “In order to obtain necessary approvals for the new road signage required for the Silvertown tunnel, a submission for the potential signs has been made to the Department for Transport.
“No charges have been finalised yet and any times and costs within the submission are indicative to allow for approval to be obtained.
“The final charges will be made ahead of the Silvertown tunnel opening in 2025 once further modelling, including assessments on concessions, are completed.”