On ME you have (subject to certain conditions) two options for income tax.
Either: you can opt to pay income tax at a fixed percentage of turnover per quarter, in which case you report your ME turnover as already taxed on your annual tax return, and no more tax is levied on that income.
Or: you can opt not to pay the flat rate tax, in which case you report your ME turnover as untaxed on your annual tax return, the “profit” (ie your ME turnover minus the abattement forfaitaire) is added to the rest of your taxable household income and the barème is applied in the normal way.
If you had an ME turnover of 7k and that was your total household income it would obviously be below the tax threshold, so it would be a bit daft to opt to pay flat rate tax on it. However I presume there is other household income so you need to first of all check if the flat rate option is open to you, and if it is, do the calculations.
However, don’t confuse income tax with social charges. The 23% you mention is your social security cotisations to cover your healthcare, etc. You pay that in any case, regardless of whether or not you opt to pay flat rate income tax (“versement libératoire de l’impôt sur le revenu”). If you opt to pay tax at the flat rate, that would be a couple of per cent on top, ie around 25%.
Full details at https://www.service-public.fr/professionnels-entreprises/vosdroits/F23267 - click on the Option pour le versement libératoire de l’impôt sur le revenu tab.