Percent first, lot second
MT5 position sizing here refuses the habit of typing 1.00 lot because that was yesterday instrument. You set the risk percent. Venasri uses the stop distance and the symbol specification on your login to land on a lot.
On a $100,000 challenge, 0.50% is $500. Five full losses at that size are $2,500, which is half of a 5% day, not the whole day. That is the gap between a sizing rule and a hope.
The bot and the hand trade use the same idea
The MT5 trading bot sizes its own orders from that percent. Manual Trade Guard uses the stop you defined so a hand entry is not naked. Neither one changes the firm daily loss. Equity Guard is still the account-level stop.
Pro at $29.99 a month includes sizing with the bot and both guards. A plain calculator, if you only want the formula, is in the calculator hub. Create an account when you want the lot applied on the live login.