Your idea about this

So, there is this guy i know that lies all the time in a strange way.
I just dont understand the meaning of his lies. He doesnt lie to gain something: everytime i lend him $10 he will just give them back or not give them back in that moment telling me exactly what happened, and then give back later, and sometimes i heard him talking with his parents "admitting" that he eventually used $1 out of $100 they gave him to do something else for a fruit juice. The same way he never lied about who he is, on the contrary he insults and underestimate himself so much that i've actually felt sorry for him many times, even if he insults himself with sarcasm. He also has a very disciplined life: wakes up at 5 am and goes running, quasi-vegan diet, fasting... I would gladly lend him my home for a week if he needed to. I would just trust him.
But from useless lies he would never gain even a cent from, he lies ALL THE TIME.
How many books do you have there? He will just add 1, or 3, or 4 to the sum for NO REASON.
How many minutes you waited there? He will double or halve the time.
How many friend you met there? He will double or halve the number.
How many cigarette did you use to smoke a day? He will oscillate between 5 and 40.
How many cm is that thing long? He will add a random number only to correct himself later (god, this one i hate the most).
Useless, pointless, compulsive lies that change nothing and that he gains absolutely NOTHING from, because he lies in both directions: he doesnt lie about his number of friends to look like a winner, in fact most of the times he halves them. He's just LYING. For NO REASON.
Why is he doing this?