Greetings!

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Hi Everyone!
I've just signed up on this and am just posting not only say Hi but also ask a question!
Currently I'm weighing about 71kgs and am about 6ft tall, sitting at, I could hazard a guess at around 8% bodyfat?
And after a few months of not weighing myself and cutting high-carb-content foods, I was shocked to see I was 71 (down from 80kg). Since I realized this (about a month or so ago) I have been trying to put on weight, to no avail. I have now set up my diary to be at about 3.5K cals per day, and was wondering if this is a good amount? As when I tried to get the app to calculate, it said I needed about 15K cals per day? Which I thought was a bit much =P
I do eat clean and don't eat processed/sugars/basically anything that tastes too good to be true :P
Any help/advice would be much appreciated!
Also, I'd rather not take knowledge without giving knowledge, so if anyone starting off is having severe trouble with weight gain (like I did, was 60kg@6ft, then "bulked" (more so just fixed my diet) and grew to 79kg over the year[which was with the help of high-carb protein shakes, which I DO NOT enjoy]), then feel free to talk to me and I will be more than happy to ATTEMPT to help :)

Thanks!