9/25/2021 GMAT Official #1 V36 Q39 620
10/6/2021 GMAT Official #2 V35 Q40 620
10/16/2021 GMAT Official #2 V35 Q44 640
10/30/2021 GMAT Official #3 V36 Q42 640
10/21/2021 GMAT Official #4 V42 Q38 660
12/22/2021 Manhattan Test #1 V36 Q44 660
12/29/2021 Manhattan Test #2 V34 Q40 610
12/30/2021 Manhattan Test #3 V34 Q41 620
I was thrilled by the jump from 440 -> 620 in a month, and saw a steady incline throughout October. Even receiving a 660 in Manhattan was a boost, as I've read that its quant questions can be trickier than the real thing. But the last two test scores have made me review the entire data differently: I think I've peaked in the mid 600s and I am struggling to get out of it.
It's generally not a good idea to compare scores across test providers. The official practice tests are your best bet, so I'd recommend additional effort in quant, followed by an official practice test before your actual GMAT.
You may want to keep at least one official practice test in reserve just in case you want or need to take the exam again.