Clarification on POT and ROI

Assuming starting from new. I place 1000.00 into my account, My bank and investment is 1000.00
Each market I target to return 10% of bank. So first target return 100.00. My first market is a selection
showing a div of 4.00 two mins before off. So the bet is placed at SP of 25.00 =Return at what ever the
sp is, add to bank if profit (profit less comm.) If it loses subtract from the bank. Rinse and repeat on
new bank. Now for the POT and ROI. A theoretical 3 weeks results!
Week 1 a net profit of 141.45 on an outlay of 660.6. So POT is 21.41%. ROI = profit on investment of
1000.00 is 14.15%
Week 2 a net profit of 115.65 on an outlay of 748.40 Total net profit for 2 weeks on an outlay of 1409.00
is net 257.1 POT is now 18.25% (257.1/1409) ROI is now 25.71% (257.1/1000.00)
Week 3 a net profit of 110.47 on an outlay of 787.00. Total net profit for 3 weeks on an outlay of 2196.00
is net 367.57 POT is now 16.74% (367.57/2196.00) ROI = 36.76% (367.57/1000.00)
If my assumptions are correct after 3 weeks my investment 1000.00 has made net profit of 367.57 =ROI 36.76%
My 3 week outlay 2196.00 for same profit 367.57 = POT 16.74.

Is this right ? If not where have I gone wrong.
Cheers