Substitutions and how they affect the match!

[Kto]

I have observed this issue, as right in the first match all three subs brought a goal during 0-3 mins after. I scored 7 goals in the second half though, nevertheless now I have some stats after 18 official games and hope, that you guys create something similar and give me tips what factors I might forget.
So we have 18 games, 56 goals scored (I observe only scores from me; many oppos dont attend and even if sometimes dont sub, and for me its a good weapon as I have a great bench, so for the simplicity just my goals; I believe there were almost no goals after opponents subs abyways, as well as no oppo goals after my subs). I do subs only in the second half so we take 37 goals scored there (yes, 19 1st half, 37 2nd, I mostly change to high press after 45 mins in tough games and bring more offensive if in troubles). Its 37 goals in 45*18=810 mins ~ 21,89 mins for a goal.
18 games ~ 50 subs (4 subs were "double" so I count them only once). Divide periods after them in three groups:
1) 0-1 mins after the sub ~ 4 goals scored
2) 2-3 mins ~ 4 goals
3) 4-5 mins ~ 6 goals
Alltogether in 0-5 mins after sub there were 14 goals, scored in 50subs*5mins=250"after-sub-mins". Its 250/14=17,85 mins for a goal.
Compared to 21,89 overall in the second half a better rate.
In 0-3 mins we have 8 goals, 3*50=150min/8=18,75 min/g.
Conclusion: so far substitution might help a bit to increase the chance to score, but needs more data.
Sidenote: Substitution gives fresh condition, can the whole team have a benefit?
Edit: not sure how to count only goals in the same minute as the sub was done, we cant really take 0 as a factor.
Edit2: no asso games