calorie deficit

i’m soooo confused on how this works. i tried calorie calculator and it says 1000 is extreme and like 1500 is easy. but i burned only 275 calories on this 4km extremely hard uphill walk ive been trying to do everyday, so that means im only meant to consume like 100-200 calories a day..?? i’m so lost like why is it so hard to just want to lose weight. everything’s always so technical. someone please simply break it all down and help me cause i’m desperate to lose 15-25kg (25 in total tho) by the end of the year or sooner.