loop JS for

Question

What is the difference

function main() { var depth = parseInt(readLine(), 10);
var a=7
var day=1
for(;a<depth;a+=7,day++){
a-=2
}
console.log(day)

with

function main() { var depth = parseInt(readLine(), 10);
var a=7
var day=1
for(;a<=depth;a+=7,day++){
a-=2
}
console.log(day)

First output 6
Second output 9

Why???

Answer 1

Initial value of a is 7 here.
Now if user enters 10 as input to depth variable then with only "<" it will run only 3 times(7,8,9 - 10<10 is false) and with "<=" it will run 4 times(7,8,9,10)