Founders while writing business plan always do mistake of bench marking with market research. Which looks too big and in the process the founders bench mark the revenue based on the market research of the industry in which they are just starting.
Founders always get into mode of questioning the revenue with market research saying when the market size is so big even if I get 10 customers I will generate enough revenue. These assumptions are now way near to ground reality.
Founders should understand the basic which is just by looking at the market size will not help in bench marking the success of there startup.
Founders also get in to primary research to understand will there be customers for there service or product, remember primary research will cost pretty much to afford at startup stage and even done so the research will be done on a sample size of 150 people and in now way there opinion can define the success or failure of your startup.
Market research is just to give clarity that yes there is scope of business for the startup, which you are planning apart from this there is no point in looking at the market size.
Founders while writing presentations also tend to get carried away with market opportunity which is complied by BIG research firms based on certain parameters and market size which is then hypothetically increase to cover the entire country.
Doing research either primary or secondary is good to understand the market acceptance and the existence of acceptance for a product or service beyond this these reports should not be considered as success to your startup.