I have 703 this week from the other two agencies and have had that score for a number of months. With the Trans Union it is always 5 to 10 points lower. I always pay at least twice as much as the minimum payment on my accounts. I have serious health problems that limit what I can eat so the food I have to purchase is expensive. That is mostly what I use my credit cards for each month. Rent keeps getting more expensive but since I have lived in the same place for 16 years and my landlord knows about my health and the fact that I am a stable tenant and am never late on rent he has tried to help me stay where I am. I haven't paid any bill late in at least 16 years. That is living on Social Security and a small retirement check. If I could get my interest rates down I could be paying down faster on the the two highest balances. I have stopped using most of my credit cards and should have another one paid off in about 4 months.
First: There is no one single way to calculate a credit score. Everybody has multiple scoring systems for different purposes. Which one they make available to you is up to them.
Second: The score is going to be based on the data at one credit bureau. Not all creditors report to all three bureaus. It makes a difference which one you use.
Start by getting all 3 full credit reports from www.annualcreditreport.com. It could be that Transunion contains information that is different from the other reports (such as, a legitimate account that is not listed on your other reports, or a mistake where your other reports are correct.)
Mistakes and inaccurate information can be appealed, but be aware that accurate information can't be removed no matter what "credit repair" companies claim.
Then, understand you have over 50 different "official" FICO credit scores. FICO offers different mathematical models. The most common is "FICO 8", and you can have 3 different FICO 8 scores if the information at the 3 credit bureaus is slightly different. Your general credit score goes from 300-850, but there are also specialty scores focused on particular lending sectors (like credit cards, mortgages and car loans) that use different mathematical models and those scores go from 250-900. And some lenders prefer the older FICO model 3 or 5. So your score can be calculated in lots of different ways.
Also, the score provided by the Turbo® app or website is a Transunion "Vantagescore" which is similar to but not the same as your FICO score. To get access to your FICO scores, you will need to buy a subscription somewhere. (Some credit cards will give you a score for free. You need to be careful what you're looking at. American Express gives an Experian FICO 8 score, Citibank gives an Equifax Bankcard FICO 8 score, and Chase gives a VantageScore, so they're all different for the same person.)
Finally, a 5-10 point difference is not really meaningful anyway. If your FCIO 8 scores are 703, 703 and 698, that all indicates you are a "good" borrower, and an average credit risk. If you needed to borrow money and a lender was going to pop your interest rate because 700 is their cutoff and one out of three scores is lower, go find another lender.