Because everyone have different risk appetitie and also bankroll capability, you will take up positions (bets) at different stakes (amount). So the best way to show PROFIT & LOSS is with UNITS instead of actual dollar value.

For example, you may place a $200 draw bet (a stake) on every match we mark; while your friend may place a $50 stake on the same matches. Because of the different stakes, the actual amount of profit/loss will be different for the two of you.

The numbers shown in Profit/Loss are UNITS, where 1 UNIT = 1 STAKE; regardless of your stake being $100/match, $120/match or $200/match. The Profit/Loss is calculated in terms of number of UNITS of STAKE profited or lost.

For example:
You entered a position of $100 for the match of TeamA vs TeamB with the Draw odds of 3.25;
you are said to have BACK X @3.25 for $100.
In this case, your STAKE = $100.
If you lose, you will LOSE $100.
If you win, you will WIN (3.25 odds - 1.00 being capital =) 2.25 x $100 = $225.
In UNIT terms, if you lose, you are -1. If you win, you are +2.25.

So, if for a certain day where you are +4.7 units, it means that if you place $120 stake/match for every match, you would have made $120 x 4.7 = $564.
If for a certain day you are down -2.8 units, then you have lost $120 x 2.8 = $336.

To work out YOUR Profit/Loss in actual dollar term ($), just MULTIPLY the UNIT with your PER-MATCH STAKE.

1X2 is a betting line, also known as Match Odds; where punters are allowed to bet on who wins, where 1 is HOME team wins, 2 is AWAY team wins and X being a DRAW.

This is different from the Asian Handicap betting line, where there is a handicap (give ball or eat ball). Under 1X2, there is no handicapping, but there is a big contrast in term of odds for favorite/underdog. Should the favorite win, you win less and when the underdog win, you win more.

Unlike traditional Bookmakers that only allow you to take position on an outcome HAPPENING (ie, Home(1) Win, Away(2) Win, or Draw(X)), betting exchanges allow you to take position BOTH on an outcome HAPPENING (by BACKING) or of an outcome NOT HAPPENING (by LAYING).

When you BACK X, you essentially put your money down on a DRAW outcome. When you LAY X, you essentially put your money down on a NON-DRAW outcome (either Home win or Away win).

This, essentially allows you to be a Bookmaker yourself (by Laying an outcome). However, the entire scope of BACK/LAY is beyond this short description. We are just interested with BACK DRAW, which means, you are betting on a DRAW outcome.