The German planners for Sealion ran off an estimated figure of 300 tons of supplies (petrol, oil, ammunition, food, first aid and other consumables) minimum for an infantry division per day of a short campaign (less than 40 days). A British infantry division usually consumed about 350-400 tons a day when engaged in a campaign, or about 15-25% more than the estimated German figure.
So for the 11 division operation that was planned, i.e two airborne and 9 infantry assault divisions, the minimum requirement was for 3,300 tons of supplies, per day.
Apart from the airborne divisions, the assault divisions were to be split up into 3 seperate beacheads, without the possibility of mutual support. 4 Divisions of 16 Army were to land in the Folkestone-St Leonards area. 2 Divisions of 9 Army were to land in the Bexhill-Eastbourne area. 3 Divisions of 9 Army were to land between Beachy Head and Brighton. The actual assaults were to be carried out only by the lead-echelons of the infantry divisions (some 6,700 men per division), totalling some 60,000 troops. Organic support formations and logistics services were to follow on in the next 9 days.
The Germans only had two main port objectives for the first week of the operation; Folkstone and Dover. Folkstone had an estimated maximum capacity of about 1200 tons per day, and was supposed to be captured on the first day. Dover had a slightly higher capacity of 1400 tons per day, and was supposed to be captured intact. Together they amount to just 2600 tons per day, or about 75% of the minimum supply requirements.
However, another part of the problem here is that neither port was expected to be taken intact, or to operate at full capacity for well past the first week of the operation. German planners assumed that sabotage by the Royal Navy and bombing by the Royal airforce would cut initial unloading capacity by 75% and keep it at around 50% capacity for the first few weeks of the operation. As a result, Folkstone was expected to handle just 150 tons per day for the first few days, building to 300 tons and then to 600 at the end of the first week. Dover was a similar story. The German Army expected to capture the port intact after 5 days, but put its maximum unloading capacity at around 800 tons per day. This is assuming that the RN didn't sink the blockships at the mouth of the harbour but that the derricks were destroyed by sabotage.
So, assumed capacity was to have been about 1400 tons a day for the first 2-3 weeks of the operation. This is around 40% of the minimum supply requirement necessary to sustain an 11 division operation, by infantry forces alone. If supply requirements were just 10% higher than anticipated no more than 4 divisions could of been supplied at minimum levels. In other-words, some 1900 tons would have to be delived to 3 seperate contested beach-heads, without port facilities, over contested beaches, with both RAF and RN interferance in operations.