As Conifold has pointed out in the comments, if two numbers are referenced in such a way that they confuse underlying concepts, then a conflation occurs. If those numbers are conceptually very closely related, but the meaning is such that the subtle distinction between them is missed, it may be an equivocation. Lastly, if numbers are used in such a way they poorly represent the central measure of a population, they may be a hasty generalization of some sort. Informal fallacies are highly context-dependent.
Natural Language is complicated and often we use synonyms, paraphrase for simplicity, or draw subtle distinctions with the connotation. In short, polysemy inheres to natural language like white to processed rice. This tends to cause problems in informal logic, where the truth values of one's propositions are highly sensitive to subtle differences in semantics. In fact, two numbers or measures can be conflated in many ways, not only by their essence, but by the mathematical relations they seek to fulfill, and this is a topic usually covered in measurement theory or specifically within a mathematical field such as statistics which has more specific fallacies such as sampling bias.
Conflation is the merging of two or more sets of information, texts, ideas, opinions, etc., into one, often in error... In logic, it is the practice of treating two distinct concepts as if they were one (emphasis mine), which produces errors or misunderstandings as a fusion of distinct subjects tends to obscure analysis of relationships which are emphasized by contrasts.8 However, if the distinctions between the two concepts appear to be superficial, intentional conflation may be desirable for the sake of conciseness and recall.
So, if one (ab)uses logic and arrives at a conclusion where two unrelated concepts are at play both with the special measure, it is conflation. That's different from equivocation. Again, WP:
In logic, equivocation ('calling two different things by the same name') is an informal fallacy resulting from the use of a particular word/expression in multiple senses within an argument.1
A good example of that might be the use of two numbers both of which are averages. As you probably know, there are many measures of central tendency.
Lastly, if the wrong numbers are used specifically within the context of making inferences about populations, it's possible those numbers can be abused in hasty generalization. Let's say someone invokes one measure in the context of describing a sample, but that number is irrelevant to drawing an inference about the population for whatever reason, then any conclusion reached would be unwarranted.
One should also bear in mind that from a logic perspective, the misuse and confusion of numbers cannot only affect the validity or strength of the argument, but the soundness and cogency of propositions depending on the effect on their truth-values (binary, multivalued, or infinite). That is to say, that a bad predication can occur in the proposition itself making the premise unsound or weak leading to an unsound or uncogent conclusion.
This is called conflation:"the practice of treating two distinct concepts as if they were one, which produces errors or misunderstandings". – Conifold